Features of oceanography and ichthyofauna composition on the Emperor Ridge

V.A. Belyaev^[36] And V.B. Darnitskiy ^[37]

1. INTRODUCTION

The area investigated is located in the east of the North-West Pacific (FAO Statistical Area 61) and includes the northwest branch of the Hawaiian Ridge (Figure 1). The Emperor Ridge is one of the largest morphological structures of the oceanic floor, separated from the Hawaiian Ridge, 5 000-5 400 m deep and about 30 nm wide. The Emperor Ridge extends 1 600 nm and is 40-140 nm wide. The length of the Hawaiian Ridge is over 1 900 nm.

USSR vessels fished on the Emperor Ridge and northern Hawaiian Ridges in 1968 after discovering abundant aggregations of pelagic armourhead (Pseudopentaceros richardsoni) in 1967. Fishing was good for several years and annual catches of pelagic armourhead peaked in the 1970s at over 150 000 t. The population abundance has been declining since 1973 and harvesting by USSR’s fleet stopped in 1976 though Japanese fishermen continued fishing for some years.

FIGURE 1. Ocean floor topography of the oceanographic survey region, R.V. Raduga and diagram of geostrophic circulation in the period 6 February-7 March 1974 near the Hawaiian Ridge

At the same time the TINRO (Pacific Research Fisheries Centre in Vladivostok, Russia) organized scientific expeditions to undertake oceanographic and biological investigations in this area. They determined that the ichthyofauna of the thalassobathyal region was poorer than that of the continental slopes of the Asian continent; shelf species were absent and bottom species were not numerous. Eighty-six bottom and near-bottom fish species occurred in trawl catches on the Emperor Ridge and 150 species north of the Hawaiian Ridge. Trawl catches taken on seamounts of the Hawaiian Ridge consisted of many species without any prevailing forms. The greater the depth the fewer the number of species. Only one or two species predominated in trawl catches in the north of the Hawaiian Ridge, which provided 95 percent of the pelagic armourhead from 1968 to 1974. From 1968 to 1977 the Russian fleet harvested 800 000 t from the summits of seamounts. Thus, the fish catch in the thalassobathyal was 29 t/km2 (Boretz and Dartnitskiy 1983) and was much higher than for other fishing grounds in the ocean (Table 1).

TABLE 1
Catch of pelagic armourhead near the Emperor and Hawaiian Ridges by USST and Japanese fishing fleet, 1968-1981 (tonnes)

The decline of pelagic armourhead abundance was accompanied by catches of increasing importance of less abundant species. For example, slender beryx, dory (Oroestomidae), rosefishes, cardinal fishes (Epigonus spp.) were significant on the Kinmei and Milwaukee seamounts. Catches of slender beryx peaked at 60 t/trawl with mean catches of 0.1-5.0 t/trawl at the Lira seamount.

Longline fishing of slender beryx on the Milwaukee seamount by Japanese fishermen began in 1972-1973. Other targets of longline fishing were butterfishes and giant skillfish (Erilepis zoniter). For example, more than ten Japanese and Korean boats fished on the Lira seamount in the summer of 1982; catches of beryx and mirror dory were 150 kg a bottom net. The Japanese trawler Aso-Maru caught 0.1 to 2.0 t/trawl during that year.

In the regions of the Emperor seamounts substantial concentrations of the epi- and mesopelagic Maurolicus were observed. Populations of Japanese mackerel (Scomber japonicus) dwell on the Kinmei and Milwaukee seamounts. Since 1973 the Japanese fleet harvested long-finned, big eye, yellow fin and blue fin tunas and marlins. In 1976 the catch of these species was 30 t/day.

2. FEATURES OF LARGE-SCALED CIRCULATION OF WATERS AND TOPOGRAPHIC EDDIES ON THE EMPEROR SEAMOUNTS

The large-scale circulation in this area is determined by the Northern Subtropic Anticyclonic Circulation. Emperor seamounts are mainly influenced by the North Pacific Current whose central jet is located along the 400 N parallel. Hydrological conditions in the north of the Emperor Ridge are a result of the interaction of subarctic waters and the Aleutian Current with seamounts. Based on findings of Japanese expeditions during 1957-1963 Ohtani (1965) reported that the Aleutian Current was divided into three branches north of the Emperor seamounts. One turns northward to the Bering Sea, the second deflects south along the axis of the ridge while the third crosses the ridge in the west moving towards Kamchatka. Expeditions by the R.V.Argo and R.V.George Kelez have found that large-scale eddies were produced in the north of the Emperor Ridge (McAlister, Favourite and Ingreham 1970). Analysis of oceanographic surveys periodically organized by expeditions of TINRO since the summer of 1968 south of the Emperor area and north of the Hawaiian Ridges confirmed the existence eddy systems of different scales above summits as well as around them. This is a typical feature of the water dynamics in this region (Darnitskiy 1979a, 1980a; Boretz and Darnitskiy 1983; Darnitskiy 1995, 2001).

Meso-scaled eddies are constantly observed in the background of the eastern transport of the North Pacific Current in the flow around the Emperor and North Hawaiian seamounts to the Hess rise. The position and structure of zonal flow in the region of the Emperor Ridge fluctuated strongly. For example, in 1979 the North Pacific Current was changed by the western countercurrent, which had not been observed earlier in this area. Both counter flows strongly meandered to produce mesoscaled eddies located between differently directed currents caused by the meridional shift of zonal mid-oceanic currents. As a result flows of the western direction of the North Wind Current were more northernly than the usual location 10 ⁰ (Darnitskiy, Boldyrev and Pavlychev 1986) (Figure 2).

Analysis of survey results from the north of the ridge by the R.F.V. Prometey has revealed that the dynamics of waters trended to a meridional location of thermohalines above ridges. Waters of the Aleutian Current are generally located southward along 170 0E where the axis of the Emperor Ridge is located. The position of the cold wedge with low salinity waters extends to 40 20' N (Darnitskiy, Boldyrev and Volkov 1984). The temperature drop in the North Subarctic Front was 4° (9-13°), that of salinity 0.8‰ (33.7-34.5‰). Thus, the dynamics of large-scaled currents during their interaction with seamounts tended to produce eddies of different scales when zonal trajectories deflected from their mean values by 5-100° and discrete current jets follow the axe of the ridge.

3. TOPOGRAPHIC EDDIES

The observed area is situated between latitudes 27-33 0N and 170 0E 180 and around longitude 178 0W and encompassed the Emperor and Hawaiian seamounts. Surveys covered the areas of the Kinmei, Milwaukee and Colahan seamounts and also six seamounts located in the 200 nm exclusive economic zone of USA. Their summits are located in depths of 160-390 m with a mean seated depths of 5 000 m. Figure 3 illustrates the dynamic topography of surface (from 1 000 dbar). An eddy structure of geostrophic currents field dominates the whole area of surveys.

It is noteworthy that there are eddy formations near the seamounts in deep layers where usually hydrophysical features are steadily distributed. Small-scale eddying is produced near summits. Small-scaled eddies occur if the horizontal scale is reduced to several miles (Darnitskiy and Mishanina 1982). For example, according to data from the background survey, the mesoscale eddy of the anticyclonic vortex of 180 x 80 nm has been observed above the Colahan seamount. The eddy was 800 m deep and the power of the eddy was strongest at a depth of 50 m where the maximum dynamic anomaly is 3.0 dyne-centimetre. The small-scale survey data (with a spatial observation of 3nm) shows that the horizontal structure of currents on the Colahan seamount is more complex. The strong anticyclonic eddy 600 m deep occurred on the southern slope of the Colahan seamount. On the eastern slope this eddy was cyclonic. The anomaly of the dynamic height in the core of the anticyclone is 4.7 dyne-centimetre; at a depth of 600 m it was 4.6 dyne-centimetre. The maximum anomaly between eddy cores was 4.8 dyne-centimetre at 100 m. In April 1976 the quasi-staggered symmetry of eddy field relative to the centre of gravity in the eddy system located on the summit of the Colahan seamount was well-pronounced. This system can oscillate relative to its centre of gravity.

Geostrophic velocities within the restricted area can increase by several cm/s to 3 m/s and more and are on average 110-160 cm/s (Darnitskiy 1980b). The numerous hydrological surveys carried out by TINRO revealed the influence of isolated seamounts of the Hawaiian Ridge on oceanological fields near the Colahan seamount under different atmosphere conditions and changing seasonal interannual and short-term conditions of the ocean and atmosphere (Darnitskiy and Zigelman 1986). The Colahan seamount is located at latitudes of 310 02' N and 1750 54' E and is a flat-topped seamount 270 m deep. The area of summit surface with a depth range of 300 m is under 3 square miles. The area level surface is around 335-460 m.

An oceanographic survey in February 1972 revealed warm and cold eddies whose numbers and strength increased with depth. At a depth of 800 m about 5 thermal eddies were observed, the temperature in their cores ranged from 5.0 to 6.2 0C with alternation of warm and cold cores. The typical diameter of eddies at the same depth was 30-50 miles. Elliptic and irregular concentric-shaped eddies were observed at different depths. At greater depths the shape of eddy was changed and their cores have displaced horizontally. The eddy structure of field is characterized by the distribution of salinity, oxygen, phosphates and silicates near the summit.

Well pronounced elliptic anticyclonic eddies with a core and top velocity to the north of the summit have been observed in August 1873. The dynamic anomaly in the core of eddy relative to peripheral field of currents was 120 din.mm. The cyclonic eddy was weaker than the anticyclone observed on the south-east slope. The eddy circulation provided the redistribution of hydrochemical properties near the seamount. For example, the maximum difference in content of silicate at the 400 m level in cores of eddies with different indexes was 300 mkg/l.

In April 1976 four eddy systems were observed down to 1 000 m (Figure 4), the deepest level of observation. Horizontal velocities in different branches of the eddies ranged from 40 to 140 cm/s with a well-pronounced asymmetry in the maximum zone. From a depth of 300 m and to the greatest horizontal extent of observations four eddy systems be observed with salinity with closed cellular isohalines.

The transition layer of minimal salinity (33.7-34.2 psu) was strongly transformed by the activity of eddies and effects of boundary zones and a intermediate salinity minimum spread in the upper horizons and sunk in the lower layers (33.7-34.2‰) in concentric boundary layer covered the top of the seamount.

The same pattern of high and low concentrations of dissolved oxygen occurred in the intermediate level lenses. Values of oxygen, which were influenced by eddying ranged from 4.25 to 6.00 ml/l. At 1 000 m fluctuations of oxygen concentration, 0.50-1.75 ml/l, were strong and had the same cellular structure. Gradients in the concentration of oxygen in the water column at 1 000 m were inclined, for example, the 5.0 ml/l isoline passed through the vertical layer from the surface to 450 m and at a depth of 100 m in the eddy core above the seamount summit. The oxygen concentration was 7.0 ml/l. In a eddy counter 3-5 miles distant the concentration of oxygen at this depth was only 3.5-4.0 ml/l (Figure 4A).

The distribution of phosphate concentrations on different horizons was also cellular. The main feature was strong upwelling of phosphates whose core was displaced south-westwards from the summit. The direction of upwelling phosphate isolines implied changes over 1000 m in the water column around seamount. The upwelling was more intense in the distribution of silicate. Isolines of silicate concentrations traverse the layer from 1 000 to 100 m almost vertically and were not attenuated at the margins of the observations. Waters from intermediate depths to the upper 100 m layer above the summit had a high concentration of silicate. The concentration of silicate ranged from 0 to 310 microgram/l near the summit at the surface. The difference of silicate concentration 1 000 m distant represented 1 130-3 000 microgram/l because of heterogeneity in the upwelling.

Surveys repeated in May-June 1977 revealed that the vertical axis of the anticyclonic eddy located above the summit can make sudden oscillations in the upper levels relative to centre of seamount when the wind direction changed. Geostrophic eddy velocities increased in June by 1.5-2 fold comparing with that found in May. The stratification of the upper 200 m layer was twice as large and in deeper layers the intermediate salinity minimum layer became thicker. In May the layer defined by the 34.1‰ isohalines was 150 m and was located 700-850 m deep. In June the layer was twice as great - 300 m and occurred at a depth of 600-900 m.

4. SYNOPTICAL CHANGEABILITY OF OCEANOLOGICAL FEATURES

Analysis of 1979 synoptical microsurveys on the Colahan seamount showned that the waters enriched by oxygen or nutrients changed, alternating in series according to the direction of the vertical velocity under the influence of counter rotating eddies.

Cyclonic circulation above seamounts results in the 500 m surface column of water being enriched by nutrients; if circulation is anticyclonic, intermediate waters are enriched by well-aerated waters, their frequent alternation results in the formation of highly productive zones because of intensification of exchange process in biotic and abiotic matter. As a result high biomasses of plankton are generated and fish productivity of surrounding waters increases (Figures 4B and 5).

The variability of eddy fields leads to significant transformations in the water mass structure and redistribution of nutrients, oxygen and planktons with approximately quasi-synoptical periodicity. This pattern of current and water mass interaction with seamounts contours occurs in relation to other seamounts of the Hawaiian and Emperor Ridges, but the intensity of upwelling differs depending on the depth and size of the seamount tops.

The increase of biological productivity in regions of seamounts provides two-dimensional dynamic formations such as Taylor eddies, which prevent the dispersion of nutrients and oxygen concentrations, and following fish spawning retains eggs and juveniles. When these are generated, their interaction with currents over seamount ridges forms quasi-ordered circulations providing habitats where lower trophic levels animals grow (Darnitskiy 1979b). Eddy intensity is strongest in the 300-500 m layer where flows interact with seamount summits. High-gradient zones can be clearly identified through temperature, salinity, oxygen and nutrients fields. High biomasses of meso- and macroplankton often occur in these zones.

Short-time fluctuations of fishing conditions occur above seamounts (Figure 6), as the result of the evolution of topographic eddy system, i.e. spatial-time transformations of eddy structure, as organisms need time to adapt to changing environmental conditions.

Quasi-two-year periodicity in changes of areas covered by positive anomalies of surface temperature were observed in the North Pacific Current at times of interannual changes of water temperature in winter during 1967-1977. Maximal values were observed in 1967, 1969, 1971-1972, 1974 and 1976, and minimal values in 1968, 1970, 1973, 1975 and 1977. In 1971 there was an anomalous warm winter and anomalous cold winters occurred in 1970 and 1977. In summer maximal anomalies were observed in 1967, 1970, 1971 and 1973. Thus, in the study the quasi-2-year periodicity in interannual changes of water temperature over 10-year period was typical for different regions of the oceans as well as in atmosphere.

5. SPECIES COMPOSITION OF FISHES ON THE HAWAIIAN AND EMPEROR RIDGES

Fishes were collected from research trips using the R.V. Academic Berg (March - April 1969 and May-June 1970), R.V. Gerakl (March-April 1975) and R. V. Equator (February-April and July-August 1976). About 500 samples were collected in an area between 27 and 37 0N and 170 0E and 178 0W.

Almost all fishes caught were identified to species or because of poor conservation of samples, by genus or family) using Kulikova (1960, 1961), Becker (1964), Belyanina (1974), Mukhacheva (1974) Parin and Novikova (1974), Parin and Sokolovskiy (1976), Fraser-Bruriner (1949), Matsubara (1955), Gibbs (1964), Grey (1964), Morrow (1964), Rofen (1966), Schultz et al. (1964) and other refences. Several new species were identified by Yu.I. Sazonov (Searsiidae) and B.I. Fedoryako (Cheilodipteridae), Institute of Oceanology Academy of Science USSR (Sazonov 1976, Fedoryako 1976).

The fish inhabiting the Hawaiian and Emperor Ridges included 172 species belonging to 56 families. More than half of all species were from six families: Myctophidae, Gonostomatidae, Sternoptychidae, Melanostomiatidae, Melamphaeidae and Bramidae. The rest of the 50 families are represented by single species (Table 2).

Table 2
Species composition of fishes on the Hawaiian and Emperor ridges

The stage of development and their habitat is indicated for each species as follows:

L - larvae, J - juveniles, A - adult, Ep - Epipelagial, Mp - mesopelagial; Bp - bathypelagial, Tb - thalassopelagial.

The most diverse species were the lanternfishes (Myctophidae) represented by 58 species belonging to 16 genuses. The most numerous were species of the genus Diaphus - 20, Lampanyctus - 10 and Myctophum - 6. Representatives of genuses of this family though less diverse however could be more abundant and sometimes made a significant contribution to the catch. According to Becker (1967) 130 species of Myctophidae from the 190 described as occuring in the Pacific Ocean are mostly distributed in subtropic and tropic waters. The geographical position of Hawaiian and Emperor Ridges and their currents are the cause of the species diversity of Myctophidae in this region.

The North Pacific Current advects species from the Western Pacific such as Diogenichthys atlanticus, Diaphus nipponensis, D. tanakae and Notoscopelus japonicus. The North Trade Current enriches this region with Myctophidae from the East Pacific e.g. Lampanyctus regalis, Triphoturus micropterus and Diaphus rafinesquei. In addition the seasonal temperature conditions favoured the presence of typical tropical species such as Myctophum orientale, M. rufinum, Diaphus fulgens and boreal species such as Electrona rissoi, Lampanyctus jordan and Ceratoscopelus townsendi.

Many species of lanternfishes occurred in our collections that have not yet been identified. For example, V.E. Becker (1967) records only 13 species of lanternfishes in the region of the Hawaiian islands, a result of the poorly investigated ichthyofauna of the Hawaiian Islands and adjacent waters. The most deep-sea samples (80 stations) were collected by the R.V. Albatross at the beginning of the 20th century (Gillbert 1905).

A similar situation occurs for other families: Gonostomatidae are represented by 13 species which include Diplophos taeuia, Maurolicus muelleri, Margrethia obtusirostra, Valencianellus tripunctulatus and Ichthyococcus elongatus. The Sternoptychidae in the region of the Hawaiian and Emperor Ridges consists of ten species of which Argyropelecus amabilis, A. ouersi, Polyipnus matsu-barai and Sternoptyx pseudobscura were newly described from this area.

It is noteworthy that range records for the Evermannellidae (Evermarmella indica and Coccorella atrata in our collections), had been limited to the Atlantic and Indian oceans (Sokolovskiy and Sokolovskaya 1975) till then. We also found rare deepwater fish such as Macrostomias paciucus, Stomias nebulosus, Pachistomias microdon and Rondeletia loricata.

6. INTERNAL WAVES ABOVE SEAMOUNTS AND THEIR INFLUENCE ON THE HYDROLOGICAL STRUCTURE OF WATERS

As a result of interaction of barotropic tidal waves with mesoscaled ocean floor irregularities above slopes and summits of seamounts internal waves are generated with tidal periods. These waves give rise to vertical transport of water masses like tidal fluctuations at sea level whose amplitude they exceed many times. As a result, seamounts periodically have lenses of intermediate water masses of different scales with well-pronounced anomalies relative to environmental background conditions.

Echo recording of commercial aggregations of marine organisms above seamounts often reflects a synchronous relation of horizontal and vertical migrations of marine organisms over a period of flood and ebb oscillations, which are mostly irregular and semi-diurnal.

Theoretical investigations have revealed that the interaction of short-term internal waves with a single cycle are characterized by the formation of isolated disturbances in amplitude in vertical velocity. The amplitude of movements of the boundary of water masses can be many orders of magnitude greater than the amplitude of tides at the sea surface. The transformation of barocline tidal waves in areas of single rise is characterized by a 2 to 3 fold increase in amplitude compared with their maximum values away from seamounts.

Data from two-hour observation from two- and three-day stations above the Hawaiian and Emperor Ridges in different seasons of 1972-1973 showed a range of temperature, salinity, dissolved oxygen, phosphate and silicate measurements were above summits of different size and seamount morphology in the upper layer of the ocean (Darnitskiy 1988a).

The experience of the commercial fleet revealed that maximum and average catches at different seamounts occurred because of different behavior of fish aggregations caused by different wave processes reflected in the diurnal oceanologic dynamics. For example, diurnal fluctuations of temperature changed by the order of 0.3 to 3.4 0C; concentrations of silicate changed from 1.75 to 370 microgram/l and of phosphate from 14 to 50 microgram/l in 0-500 m layer.

In winter diurnal fluctuations of temperature in the upper quasi-homogenous layer were not significant, ranging from 0.34 to 0.49 0C. However, at depths of 75-100 m the amplitude of fluctuations peaked at 2.6-3.4 0C and was 2.1 0 at 150 m. Concentrations in many cases coincided in time but did not match the period of dissolved oxygen extremes connected with processes of biochemical consumption. Seamounts are characterized by high amplitude of daily changes of oceanographic properties. In winter, maximum amplitudes of water temperature occur in intermediate depths of 100-150 m; in summer maximum amplitude are displaced by 50-76 m because of the development of the seasonal thermocline.

Submarine observations of the Mid-Atlantic ridge show that aggregations of fish respond to tidal water movements changing their depths and their areas relative to bottom relief.

Rossby waves, wave disturbances on a planetary scale, can transport energy to seamounts by small-scaled topographic waves or small-scaled eddies in the geostrophic circulation field near seamounts on the Hawaiian Ridge (Darnitskiy and Mishanina 1982, 1987; Jansons and Johnson 1988). The transformation of large scale wave-eddy formations influences redistribution of oceanographic properties and marine organisms on the surface as well as in the water column near seamounts depending on the intensity of these processes and local features of the bottom relief.

Analysis of data from 10-day stations above the Lire seamount (36¢ª48' N, 171¢ª22' E) in the system of the Emperor Ridge has revealed waves with larger periods than daily tidal ones (Darnitskiy 1988b). During the period 23 June-3 July 1982 well-pronounced maxima of oxygen at depths of 30-50 and 200-300 m were observed with the highest changes (0.75-1.32 ml/l, s.d. ó = 0.18-0.28) in the depth range of 50-100 m. The second maximum of amplitude (0.56-0.60 ml/l, ó = 0.13-0-18) was observed in the depth range of 300-400 m. The third peak in the amplitude of changeability (0.65 ml/l, ó = 0.12) occurred at a depth of 200 m. The convergence of peak amplitudes of oxygen concentration in the vertical dimension is explained by periodically repeated vertical displacements of water masses along slopes of seamounts under the influence of wave processes i.e. topographic Rossby waves and Kelvin waves (Darnitskiy, Mishanina 1987, Darnitskiy 1988b).

The vertical haline structure near the Lira seamount is characterized by two extremes of changeability related to higher salinity at the surface (34.6-34.9‰) in the first case and an intermediate layer of lower salinity (34.02-34.13 psu) at the depths of 45-650 m in the second case. The amplitude of salinity changeability peaked in the upper layer of 0-100 m (0.23-0.29‰, ó = 0.06-0.07) and in the layer 200-300 m (0.19-0.23‰). Peaks of concentration of salinity amplitudes did not match depths of extremes on vertical lines of salinity and were caused by wave phenomen. The quasi-cyclical character of changeability in structure of salinity was also found in the vertical change of oxygen. In the upper 0-100 m layer, a 1-3 day periodicity was found during a 10-day period of observation. At 200-400 m depth, an intense deep-sea disturbance occurred on the fifth day after the upwelling of deepwaters occurred three times over the preceding 10-day period. Vertical displacements of isochalines reached 100-110 m in the intermediate layer at depths of 100-400 m in the second half of the observations. Thus, the deep structure of water mass changeability is more complex than in the upper nearly uniform layer!

Continuous 9-month monitoring of temperature and currents near the Bermuda islands allowed observations of internal Kelvin waves with periods of 1.1-1.9-2.2-3.8 days intercepted by the island (Hogg 1980). Methods of observations in the Emperor and Hawaiian regions did not determine wave periods. However, it is evident that scales of internal wave periodicity are large, from 4-day tidal oscillations to 3-day Kelvin and Rossby waves. These data coincide with the results of Hogg’s observation in the region of the Bermudan islands.

7. CONCLUSION

i. The dynamics of large-scale currents interacting with seamounts are characterized by generation of eddies of different scales and deviation of current trajectories by 5-10 0 along the axis of ridge.

ii. Topographic cyclogenesis^[38] is stronger in subsurface and intermediate water masses interacting with seamount summits. In addition inverse eddies can be observed.

iii. Deepwater eddies are well-pronounced in hydrochemical structure to depths 1 000-1 500 m and generates dynamic heatons.

iv. Surveys by the R.V. Vityaz in 1956 found Japanese fishermen already knew of the fish aggregations on seamounts in the 1950s long before large-scale harvesting on the Emperor and Hawaiian Ridges began.

v. Biological productivity is increased by internal waves located near seamounts that are blocked by seafloor relief and augment amplitudes many times, sometimes orders of magnitude, greater than background values.

vi. The observed ichthyofauna consisted of 172 species belonging to 56 families.

vii. More than half of all species found (55.8 percent) belonged to six families.

viii. Seamounts are zones of high productivity, which are related to coastal ecosystems through current systems.

8. LITERATURE CITED

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The census of marine life: community access to basic science

K. Yarincik and R.K. O’Dor
Census of Marine Life Secretariat
1755 Massachusetts Ave. NW
Washington, DC 20036 USA
<kyarincik@coreocean.org>

1. INTRODUCTION

Investments made to explore space and distant planets are far greater than what have been spent to study oceans right here on earth. Is it any wonder then, that we know so comparatively little about them? Perhaps the most striking gaps in our knowledge of the oceans are in what lives there. Answers to questions of where and how many are needed, but we do not even know for certain what species are there. Science has only identified about 200 000 of possible millions of marine species believed to exist (O’Dor 2003). From what we do know, at the genetic level, the oceans contain the vast majority of all biodiversity, a resource whose importance society has only recently begun to realize. Efforts to successfully exploit, and sustain, marine biodiversity are hindered by our lack of knowledge.

Assessing what lives where in the oceans was once an impossible dream, but new technologies available to science make such an endeavor realistic today. The Census of Marine Life is a ten-year international research programme that takes advantage of this opportunity to assess and explain the diversity, distribution and abundance of life in the oceans - past, present and future. Because the ocean habitats span from the only intermittently underwater to depths of over 10 000 m, so the approaches to studying the ocean’s life also varies. The Census tackles the unknown by dividing the ocean into six realms: human edges, hidden boundaries, central waters, active geology, ice oceans and the microscopic. Strategically, these realms are sub-divided into zones based on the types of technologies used to survey their marine life (Figure 1). There are currently seven zonal field projects underway and several more in development. These projects, regional to global in scale, are demonstrating techniques and standardizing protocols for observation of life in the oceans. Between 2005 and 2010, the Census will encourage additional sampling in all oceans using these protocols to achieve global comparison (Decker and O’Dor 2002).

Additional research components support the field projects to address issues of time and to develop tools for serving and analyzing biodiversity data. The History of Marine Animal Populations project is uncovering ‘baselines’ using a unique interdisciplinary approach to interpret changes in marine populations as recorded in historical archives. Computer models are incredibly useful for synthesizing and interpreting biodiversity data. The Future of Marine Animal Populations develops and tests computer models to facilitate analyses of the historical and current state of marine species and their interactions with one another, as well as enabling synthesis of a variety of data types and more reliable predictions on how marine populations may respond to stress from fishing and climate change. Finally, in order to archive and serve data and analytical tools, the Census is supporting the development of the Ocean Biogeographic Information System, a web-based, publicly-accessible portal to global geo-referenced information on accurately identified marine species.

2. THE DEEP SEA

While the Census of Marine Life includes both coastal and deep ocean environments, for the purposes of this paper the focus will be on the deep-sea projects (Figure 2). The deep sea poses particular challenges to research because of its remoteness and the environmental conditions associated with that environment. So little is currently known about these ecosystems that estimates as to the necessary - or even possible - sampling resolution are difficult at best. The sediments of the deep-ocean floor, for example, are one of the most species-rich marine habitats; undescribed species are discovered in every expedition. Expeditions to date, though, have barely touched this expansive environment, making it also one of the least well known with estimates of species ranging from less than one million to five million (Grassle 2001).

The deep-sea projects of the Census are encompassed under several of the different realms. The first is the "hidden boundaries", interfaces between major geologic boundaries that form unique habitats, such as the sediments of the abyssal plains, separating the basin of water from the oceanic crust. The project entitled Census of Diversity of Abyssal Marine Life, or CeDAMar, is aimed at documenting actual species diversity globally in abyssal plain sediments and determining what the controlling factors of biodiversity in the abyssal plains may be. For example, what is the role of primary production in the surface waters on deep diversity? Like all Census projects, CeDAMar will standardize approaches to surveying deep benthic marine life so that meaningful comparisons can be made between sites and studies. Target species are primarily small organisms like protists, crustaceans, and worms, in which the sediments are rich.

The seafloor, however, cannot be solely characterized by these wide expanses of minimal topography. New earth has also been forming for billions of years and creating the isolated habitats of the realm of "active geology." Because of their isolation these habitats offer tremendous opportunity for exploration, both in terms of locating the existence of a site and of studying its unique - and often highly endemic - fauna. Hydrothermal vents were not discovered until the late 1970s, and with that came the discovery of symbiotic tube worms. Scientists learned that this entirely new ecosystem received energy chemosynthetically from hydrogen sulfide emitted in the black "smoke" from the vents independent of surface organic production. Our understanding of hydrothermal vents and other chemosynthetic ecosystems (cold seeps, whale carcasses, sunken wood and areas of low oxygen associated with subduction zones) is limited to studies of only a few sites around the globe; there is still much unknown. The Biogeography of Chemosynthetic Ecosystems (ChEss) project will assess the diversity, distribution, and abundance of the species in chemosynthetic ecosystem and explain the differences and similarities from place to place at a global scale. ChEss will look at potential processes controlling biodiversity, such as larvae dispersal, topography and sea floor spreading (Van Dover et al. 2002).

Another product of active geology is seamounts. Many are geological ghosts of volcanoes and like vents and seeps, seamounts are often geographically isolated, providing a great opportunity to substantially increase our understanding of biogeography by looking at the similarities and differences in the communities between separate seamounts. Of the 30 000 or more seamounts around the world, only about 200 have been sampled. From those surveys, almost half of the species collected were new to science and likely to be endemic to their particular ecosystem. Increased exploitation of seamount fauna has put pressure on scientists to study seamounts. The Census has begun the development of a global seamount project that will synthesize existing biodiversity knowledge and direct future field efforts towards a comparative ecology of seamounts, categorizing communities and developing proxies for generalized models that will enable us to predict properties of unexplored seamounts, a capability urgently needed for effective management of fisheries on seamounts.

Above the seafloor is the oceanic dark zone of the "central waters" where the Census project known as MAR-ECO (Patterns and Processes of the Ecosystems of the Northern Mid-Atlantic) aims at describing and understanding the patterns of distribution, abundance, and trophic relationships of the organisms in the deep pelagic, near-bottom and epibenthic habitats of the North Atlantic. Even in the dark zone, most animals rely on nutrients from primary production near the surface, which fall through the water column as marine snow. Images collected by the MIR submersibles on a recent MAR-ECO expedition to the Charlie Gibbs Fracture Zone (Mid-Atlantic Ridge) revealed surprisingly high concentrations of marine snow at over 4000 m depth indicating the environment there may be able to sustain a high diversity of species. MAR-ECO surveys focus on macrofauna and megafauna, including fish, crustaceans, cephalopods and gelatinous zooplankton. Because of the depth and the often rough terrain associated with mid-ocean ridges, many traditional sampling methods (e.g. trawling) are not an option, so MAR-ECO must utilize innovative methods and technology to study and map the distribution of life there.

3. ACCESS TO DATA

While the pursuit of a global understanding of marine biodiversity is a laudable goal for the scientific community, there is a crucial societal need to implement effective policies to manage marine resources. The major advancement in basic scientific knowledge that will result from the Census, therefore, will be particularly useful if made publicly available. The Census requires this of all its projects and to facilitate the process, is supporting the development of the Ocean Biogeographic Information System (OBIS, <http://www.iobis.org>), a single web-based portal to geo-referenced data on accurately identified marine species collected not only by the Census but from a federation of data providers around the world. The federation ensures inter-operability, but each data contributor separately maintains the datasets and intellectual ownership over the data. OBIS is the marine component of the Global Biodiversity Information Facility.

The development of this dynamic, digital atlas began in 2000 with the funding of a feasibility demonstration to make interoperable eight authoritative data sets of particular taxonomic groups. As of November 2003, OBIS enables simultaneous searches of 19 inter-operable databases, which, in addition to the museum collections, include taxonomically resolved, geo-referenced datasets from genetic studies, time-series, continuous plankton recorders, the Food and Agriculture Organization’s Catch and Aquaculture Production and, in the future, industry (e.g. petroleum, bioprospecting).

The data collected by modern ocean science has made OBIS a valuable resource for scientists and managers to identify what is currently known to live and where it lives in the oceans, but with the inclusion of the Census’s historical and modeling components, it enables comparisons over hundreds of years. The History of Marine Animal Populations contributes ‘outside-the-box’ approaches to marine research, amassing taxonomically resolved distribution and abundance information from 100 to 500 year-old archives of fishing logs, tax records and recipes (Holm, Smith and Starkey 2001). The result is a historical baseline against which scientists can evaluate current distribution and abundance of marine populations.

With a baseline, projections about the future become more reliable. Though OBIS offers some modeling techniques useful for basic prediction, particularly in terms of marine invasions and, to a certain extent, climate change, the Future of Marine Animal Populations (FMAP) will test and contribute new cutting-edge biodiversity models to the system. Initial models will focus on interpreting migration patterns from tagged animals, species interactions, and predictions of the effects of climate change and fishing pressure on populations (Worm et al. 2003).

OBIS is already a powerful tool with over one million records of some 5 000 unique marine species, which can be downloaded directly or overlaid on maps of physical oceanographic parameters. Based on the scheduled addition of datasets, OBIS will put at least 10 million records of all known species and their location online by 2007.

4. GLOBAL COOPERATION

A global programme requires global participation. In November 2003, researchers from 50 countries were involved in the Census. But, in addition to willing researchers, the success of the Census depends on global partnerships in governance and funding. An international Scientific Steering Committee oversees the conceptual goals and direction of the programme. They have designed the Census in such a way that its products will be of benefit to a wide range of users. The overall estimated cost of the programme is US$1 billion, making the contribution of a wide range of sponsors important. Though there is some international funding available for this research, much of the sponsorship must be generated at national levels from traditional sources such governmental agencies and philanthropic foundations. Sponsorship through funding or other services can also come from novel programmes led by industry that have vested interests in marine life (e.g. fishing, pharmaceuticals) or whose work in the ocean affects ecosystems (e.g. mining, petroleum production).

The task of raising funds for Census research is enormous and the ten-year timeframe makes it urgent. To accomplish it, national and regional implementation committees are being established around the world. As of November 2003, implementation committees are operating in Australia, Canada, Europe, Japan, South America and the United States. Developments toward creating a committee are underway in Russia, China, the Caribbean, the Indian Ocean, Sub-Saharan Africa and the WESTPAC region. There is interest in the New Zealand/South Pacific region though appropriate mechanisms must be identified.

These committees are comprised of scientists as well as representatives from conservation, management, industry and other ocean stakeholders to ensure effective implementation of the programme with legacies that will be understood and appreciated by global society. Even with the majority of the effort still ahead, the successes to date in engaging and organizing the scientific community makes Census a proven demonstration of the value of partnership and cooperation.

5. LITERATURE CITED

Decker, C.J. & R.K. O’Dor 2002 A Census of Marine Life: Unknowable or Just Unknown? Oceanologica Acta. 25(5): 179-284.

Grassle, J.F. 2001. Marine ecosystems. In Levin, S.A. (Ed) 2001. Encyclopedia of Biodiversity. Volume 4. Academic Press: 4666pp.

Holm, P., T.D. Smith & D.J. Starkey 2001. The Exploited Seas: New Directions for Marine Environmental History. International Maritime Economic History Association/Census of Marine Life: St. John’s, Newfoundland, 216pp.

O’Dor, R.K. 2003. The Unknown Ocean: Baseline Report of the Census of Marine Life Program. Consortium for Oceanographic Research and Education: Washington DC, 28pp. Available at <http://www.coml.org/baseline>.

Van Dover, C.L., C.R. German, K.G. Speer, L.M. Parson & R.C. Vrijenhoek 2002. Evolution and biogeography of deep-sea vent and seep invertebrates. Science. 295: 1253- 1257.

Worm, B., H.K. Lotze & R.A. Myers 2003. Predator diversity hotspots in the blue ocean. Proceedings of the National Academy of Sciences. 100(17): 9884-9888.

Patterns and processes of the ecosystems of the Northern Mid-Atlantic (MAr-eco project) - an international census of marine life project on deep-sea biodiversity

O.A. Bergstad and T. Falkenhaug
Institute of Marine Research, Flødevigen Marine Research Station
N-4817 His, Norway
<oddaksel@imr.no, tonef@imr.no>

1. INTRODUCTION

Despite the wide distribution and extensive area of mid-ocean ridges (see e.g.. Garrison 1993), relatively few previous investigations have been dedicated to the study of the animal communities inhabiting these vast areas of the world ocean. Ridges may have characteristic faunas, and they may also significantly influence the processes such as intercontinental migration and dispersion affecting slope and shelf biota. Compared with the continental shelf and coastal environments, the ecosystems of the mid-oceanic ridges are poorly known and exploratory activity will provide new knowledge on both previously described and undescribed species. However, providing well-documented new information on how mid-oceanic ridge communities are structured and sustained is a challenging task.

The MAR-ECO project (Bergstad and Godø 2002, <http://www.mar-eco.no/>), whose objective is the study of the mobile macrofaunal communities associated with the Mid-Atlantic Ridge between Iceland and the Azores, is one of the field projects of the Census of Marine Life programme (CoML, <http://www.coml.org>). The overriding goal is to describe and understand the patterns of distribution, abundance and trophic relationships of the organisms inhabiting the mid-oceanic North Atlantic and identify and model ecological processes that cause variability in these patterns. The study will focus on pelagic and benthic macrofauna and use innovative methods and up-to-date technology to map distributions, analyse community structure, study life histories and model trophic relationships.

2. BACKGROUND

The Mid-Atlantic Ridge (MAR) is the spreading zone between the Eurasian and American plate (Figure 1) is a part of a world-wide system of oceanic ridges. As a result of volcanic and tectonic processes, the ridge is continually being formed as the two plates spread at a rate of about 2 cm/yr. Between Iceland and the Azores the ridge extends over 1500 nm, and it is characterized by a rough bottom topography comprising underwater mountain chains, a central rift valley, recent volcanic terrain, fracture zones and seamounts. The MAR has an important influence on the deepwater circulation of the North Atlantic, partly separating deepwaters of the eastern and western basins.