Distribution of Calanus species in Kongsfjorden, a glacial fjord in Svalbard

The distribution of Calanus species was investigated in Kongsfjordenin summer of 1996 and 1997. In both years Calanus finmarchicusand Calanus glacialis dominated, although the boreal C. finmarchicuswas more abundant than the Arctic C. glacialis in 1997. Thiscoincided with a 2°C higher water temperature at 50 m in1997, indicating stronger influence of Atlantic origin waterthat year. Advected Calanus finmarchicus occurred in deep andsubsurface layers of the outer fjord in 1996 (200 ind. m^-3,mainly CIII). A less abundant local population aggregated insurface layers of the inner fjord (100 ind. m^-3). Similarly,advected C. finmarchicus occurred in subsurface layers in 1997(446 ind. m^-3, mainly CIII and CIV) and a local population insurface layers (183 ind. m^-3, mainly CI). Calanus glacialisin 1996 aggregated as CII and CIII in the deep layers of theouter fjord (272 ind. m^-3), whereas CIII–CV were abundant(216 ind. m^-3) in cold surface waters of the inner fjord. In1997 C. glacialis (mostly CIII–CV) was more abundant inthe outer than in the inner part of the fjord (40 and 192 ind.m^-3, respectively). Within Kongsfjorden, Calanus finmarchicusneeds one year to complete its life cycle, whereas Calanus glacialisneeds two. Calanus hyperboreus seems to be an expatriate inthe fjord system.     

Seasonal variations in abundance, development and vertical distribution of Calanus finmarchicus, C. hyperboreus and C. glacialis in the East Icelandic Current

The seasonal variation in abundance and development of Calanusfinmarchicus, Calanus hyperboreus and Calanus glacialis in relationto hydrography and chlorophyll (Chl) a was studied in the Arcticwaters of the East Icelandic Current to the north-east of Icelandfrom March 1995 to February 1996. The sampling was carried outat approximately monthly intervals on a transect of five stationsextending from 67°00'N, 13°55'W to 68°00'N, 12°40'W.In April, May and June, vertical distribution was also investigated.Spring warming of the surface waters began in May, with maximumtemperatures recorded in August (~5°C, mean for uppermost50 m). Below 75 m, temperature remained at <0°C throughoutthe year. The spring bloom of phytoplankton started in earlyMay and the highest Chl a concentrations were measured duringlate May to early June (~1 mg Chl a m^-3). Calanus finmarchicusdominated in terms of numbers (~75%), while C. hyperboreus dominatedbiomass (~76%). Calanus glacialis occurred only in low numbers(~1%) and was only a small portion of biomass (~0.7%). The abundanceof all species was low during the winter and peaked once duringsummer: C. finmarchicus in July (~16 000 ind. m^-2) and C. glacialisand C. hyperboreus in June (~370 and ~7700 ind. m^-2, respectively).The biomass of C. finmarchicus had two maxima, in April (~1.9g m^-2) and July (~1.5 g m^-2), while C. hyperboreus peaked inJune (~12.3 g m^-2). Calanus finmarchicus was estimated to spawnin early May at about the start of the spring bloom, while C.hyperboreus spawned prior to the spring bloom, in late Februaryto early March. On the basis of copepod stage distribution,C. finmarchicus was considered to have a 1-year life cycle andC. hyperboreus at least a 2-year life cycle.     

Evolution of Nemertesia hydroids (Cnidaria: Hydrozoa,Plumulariidae) from the shallow and deep waters of the NE Atlantic and western Mediterranean

Moura, C. J., Cunha, M. R., Porteiro, F. M., Yesson, C. & Rogers, A. D. (2011) Evolution of Nemertesia hydroids (Cnidaria: Hydrozoa, Plumulariidae) from the shallow and deep waters of the NE Atlantic and Western Mediterranean. —Zoologica Scripta, 41, 79–96. Hydroid species from the genus Nemertesia develop some of the largest and most complex hydrozoan colonies. These colonies are abundant and ecologically important in both shallow and deep waters worldwide. Here, we analyse the systematics of most Nemertesia species from the NE Atlantic and Mediterranean using morphology and phylogenetic inferences of 16S rRNA haplotype data. Phylogeographical analysis revealed multiple movements of taxa to and from the Mediterranean after the Messinian salinity crisis through shallow and deep waters. The nominal species Nemertesia belini and Nemertesia antennina revealed multiple genetic lineages representing cryptic species diversity. Molecular phylogenetic evidence was supported by consistent phenotypic differences between lineages, and three and seven putative species were resolved within the N. belini and N. antennina complexes, respectively. Three putative species of the N. antennina complex found at different seamounts of Azores grouped in a clade clustered amongst the other four cryptic species present at neighbouring bathyal localities of the Gulf of Cadiz. These cryptic species, mostly from the deep sea, form a clade distantly related to the typical N. antennina from European coastal waters. Depth or environmental correlates of depth seem to influence the reproductive strategies of Nemertesia colonies and ultimately speciation. In particular, speciation of these hydroids must have been influenced by hydrography, habitat heterogeneity, isolation by distance and larval dispersal capacity. The deep sea is shown as an important environment in the generation and accumulation of lineages that may occasionally invade coastal waters in the NE Atlantic. Glacial cycles of cooling, along with changes in sea level, and eradication of some coastal faunas likely facilitated speciation and evolutionary transitions from deep to shallow waters.     

Evidence of artisanal fishing impacts and depth refuge in assemblages of Fijian reef fish

Protection from fishing generally results in an increase in the abundance and biomass of species targeted by fisheries within marine reserve boundaries. Natural refuges such as depth may also protect such species, yet few studies in the Indo Pacific have investigated the effects of depth concomitant with marine reserves. We studied the effects of artisanal fishing and depth on reef fish assemblages in the Kubulau District of Vanua Levu Island, Fiji, using baited remote underwater stereo-video systems. Video samples were collected from shallow (5–8 m) and deep (25–30 m) sites inside and outside of a large old marine reserve (60.6 km², 13 years old) and a small new marine reserve (4.25 km², 4 years old). Species richness tended to be greater in the shallow waters of the large old reserve when compared to fished areas. In the deeper waters, species richness appeared to be comparable. The difference in shallow waters was driven by species targeted by fisheries, indicative of a depth refuge effect. In contrast, differences in the abundance composition of the fish assemblage existed between protected and fished areas for deep sites, but not shallow. Fish species targeted by local fisheries were 89% more abundant inside the large old reserve than surrounding fished areas, while non-targeted species were comparable. We observed no difference in the species richness or abundance of species targeted by fisheries inside and outside of the small new reserve. This study suggests that artisanal fishing impacts on the abundance and species richness of coral reef fish assemblages and effects of protection are more apparent with large reserves that have been established for a long period of time. Observed effects of protection also vary with depth, highlighting the importance of explicitly incorporating multiple depth strata in studies of marine reserves.     

The occurrence of Calanidae species in waters off Argentina

As food of planktivorous fish and likely good predictors of natural perturbations, members of the family Calanidae are recognised to be key species in ecosystems worldwide. The distribution and seasonal relative abundance of the Calanidae species occurring in the Argentine Sea were reviewed from published and unpublished data collected over the last three decades. Species are also figured in order to elucidate any possible taxonomic uncertainty. Calanoides cf. carinatus, Calanus australis and Calanus simillimus are the most abundant calanids in the region. The former two species typically inhabit inner and middle shelf waters decreasing offshore, while Calanus simillimus is distributed in the middle and outer shelf, its abundance increasing towards the shelf-break. The southern limit of the distribution of Calanoides cf. carinatus appears to be 46° S. Calanus australis is the most common large copepod in coastal and inner shelf waters off southern Patagonia. Neocalanus tonsus and Calanoides patagoniensis are a much rarer species. The latter is recorded in the southwestern Atlantic, for the first time, immediately east of Magallanes Strait and the Beagle Channel. The taxonomic status and worldwide biogeographic distribution of the region's calanids are briefly described and the patterns identified off Argentina are discussed in relation to the major hydrographic characteristics.     

Impact of warm water advection on the winter zooplankton community in an Arctic fjord

The west coast of Spitsbergen is influenced by water masses of Atlantic and Arctic origin. During the winter of January–April 2006, water temperatures on the West Spitsbergen Shelf were ∼3°C warmer than typical winter conditions, leading to a coastal sea ice cover of reduced thickness, extent and duration. A sediment trap deployed from September 2005 to May 2006 in the outer basin of Kongsfjorden (NW Spitsbergen) at a depth of 115 m has provided a continuous winter time-series of zooplankton during a period of rapid increase in water temperatures. Prior to an anomalous and prolonged influx of warm Atlantic water (AW) starting at the end of January, the trap samples were dominated by the boreo-Arctic copepod Metridia longa. Species that increased in abundance during the influx included late stages of Calanus finmarchicus, C. glacialis, C. hyperboreus and Paraeuchaeta norvegica. The early introduction of shelf populations into the fjord, and thus increased copepod biomass relative to typical winter conditions with little advection, has implications for the marine pelagic food web and pelagic-benthic coupling.     

Mesozooplankton distribution in northern Svalbard waters in relation to hydrography

We investigated the distribution of mesozooplankton in waters north of Svalbard (north of 78°50′N) at 38 stations in August and September of 2002, 2003 and 2004. The zooplankton community was numerically dominated by copepods (58–98% of the total abundance). Zooplankton abundance ranged from 115 individuals m⁻³ at the northern most location to 12,296 individuals m⁻³ on the shelf. Cluster analysis revealed four different groups with distinct geographic integrity that were identified by variation in species densities rather than by variation in taxonomic composition. Water temperature and salinity differed significantly between the different cluster groups indicating that part of the observed variations in species distribution relate to differences in hydrography. Numerous significant regressions between zooplankton abundance at species level and hydrographical parameters suggest that variability in water masses has measurable effects on zooplankton distribution and species composition in the study area.     

The distribution and abundance of scyphomedusae (Scyphozoa) of the family Ulmaridae in the pelagic zone of the Sea of Okhotsk and the Sea of Japan

The distribution and abundance of jellyfish of the family Ulmaridae was studied based on the data of trawl surveys conducted in the Sea of Okhotsk (1998–2006) and the Sea of Japan (2003) in the fall. The jellyfish Aurelia aurita mainly inhabits the waters of the Sea of Japan, while in the Sea of Okhotsk small quantities of this species were recorded in southern areas, and solitary individuals, off North Sakhalin. Aurelia limbata tends to shelf waters of the Sea of Okhotsk, being less abundant in the southern deepwater area and in the Sea of Japan. Phacellophora camtschatica, in contrast, aggregates mostly over deep basins, whereas in shallow areas a significant quantity of this species was found only off West Kamchatka. In the northern Sea of Okhotsk, the species A. limbata dominated in biomass and abundance among Ulmaridae. During the studied period, its biomass varied from 27 to 803 kg/km² and its abundance varied from 69 to 1706 ind/km². In the southern Sea of Okhotsk, as a rule, P. camtschatica prevailed (1–16 kg/km² and 6–46 ind/km²). In the Sea of Japan, the most abundant species was A. aurita (29 kg/km² and 104 ind/km²). The jellyfish size structure in catches is presented.     

Zooplankton in Svalbard fjords on the Atlantic–Arctic boundary

Zooplankton abundance and community structures were studied in three west Spitsbergen fjords at the beginning of the warm phase, which seem to have entered in 2006. Sampling was conducted in summer 2007 at stations distributed along transects in Hornsund, Isfjorden and Kongsfjorden. Variations in zooplankton standing stocks and community structures (assessing taxonomic diversity and zoogeographical affiliations) were analysed in relation to the environmental variables using multivariate techniques. The hydrographic conditions in Hornsund were influenced by the cold Arctic Water, whereas those in Isfjorden and especially in Kongsfjorden were, to a greater extent, under the influence of the warm Atlantic Water. High abundances of both meroplankton and holoplankton organisms were observed in Kongsfjorden, with high contributions of boreal and ubiquitous species (Calanus finmarchicus and Oithona similis, respectively). In Hornsund at the same time, the zooplankton consisted mainly of boreo-Arctic and Arctic species, the abundances of which were comparable along the West Spitsbergen Shelf. Our results indicate that the difference in hydrography had measurable effects on the zooplankton community in the study area. Furthermore, by comparing regions of contrasting oceanographic conditions, we present evidence as to how the zooplankton structure will change in the Arctic ecosystems if the warming trends continue to operate with the same dynamics. The advection of Atlantic waters to the Arctic seas may lead to changes in zooplankton structure, with increased abundance and contributions of boreal and small ubiquitous species. The ‘warmer Arctic fjords’ scenarios may also induce more rapid development of both holoplankton and meroplankton populations and, consequently, modify the trophic interactions in plankton communities.     

Composition and distribution of zooplankton in the Laptev Sea and adjacent Nansen Basin during summer, 1993

Zooplankton composition and distribution were investigated on the Laptev Sea shelf, over the continental slope and in the adjacent deep Nansen Basin during the joint German-Russian expedition “Arctic 93” with RV Polarstern and Ivan Kireyev in August/September 1993. In the shelf area biomass decreased from west to east with the lowest values in the area influenced by the Lena river runoff. A gradual increase of biomass from the shallow to the deep area correlated with water depth. Total biomass ranged between 0.1 and 1.5 g m⁻² on the shelf and 4.7 and 7.9 g m⁻² in the adjacent Nansen Basin. On the shelf Calanus glacialis/finmarchicus dominated overall. The contribution of brackish-water taxa was low in the west, where high salinity and southward currents from the Arctic Basin supported a marine neritic community, but on the southern and eastern Laptev shelf, in the areas of freshwater influence, brackish-water taxa contributed up to 27% of the total biomass. On the slope and in deep areas a few large Arctic copepod species, Calanus glacialis, C. hyperboreus and Metridia longa, composed the bulk of biomass and determined the pattern of its vertical distribution. The export of Calanus species from the Nansen Basin onto the Laptev shelf appears to be of great importance for the shelf communities. In turn, the eastern outer shelf and slope area of the Laptev Sea are thought to have a pronounced effect on the deep basin, modifying the populations entering the central Arctic. Received: 25 March 1997 / Accepted: 18 July 1997     

Seasonal and interannual variation in abundance of Calanus finmarchicus (Gunnerus) and Calanus helgolandicus (Claus) in inshore waters (west coast of the Isle of Man) in the central Irish Sea

The seasonal and interannual variability in abundance of Calanusfinmarchicus and Calanus helgolandicus in the Irish Sea wasexamined on the west side of the Isle of Man (central IrishSea) between 1995 and 2001. There was considerable interannualvariability in abundance of both species that was greater thanthat seen in adjacent seas. In general, maximum abundance occurredbetween May and July each year with C. finmarchicus tendingto occur earlier in the year than C. helgolandicus. There wasa significant difference in interannual maximum abundances inthe area (14–18 stations treated as replicates) with mostyears having a low abundance and one year a relatively highabundance. The maximum abundance of C. finmarchicus (1996) coincidedwith a low (negative) index value of the North Atlantic Oscillation(NAO), and with a high abundance of young gadoids (cod, haddockand whiting) in the water column and a large settlement of plaice.A high abundance of C. helgolandicus coincided with a relativelyhigh (positive) index value of the NAO in 2000. The magnitudeof interannual and seasonal variability in abundance was inclose agreement with data from an inshore area (Port Erin Bay,Isle of Man) between 1907 and 1920. As with many Calanus populations,the adults in both species were predominantly female. As shownpreviously, Calanus is not one of the numerically dominant copepodspecies in the Irish Sea. However, the presence of young stagesof Calanus within the central Irish Sea suggests that it mustsupport a breeding population.     

Distribution of the under-ice mesozooplankton in the Kara Sea in February 2002

Mesozooplankton distribution was investigated under the sea ice in the Kara Sea at five stations in February of 2002 by Juday net hauls. Copepods dominated the mesozooplankton community, accounting for 46–88% of the total abundance and 68–99% of the biomass. Oithona similis was the most abundant species in Yenisei Bay, being present with all age stages (including egg-carrying females). For the first time, Oithona atlantica (CIII–CV copepodites, females and males) were found in the southeastern Kara Sea. In the southern part, Copepoda nauplii prevailed in terms of total abundance while the mesozooplankton in the northwestern part was entirely dominated by older stages of Pseudocalanus minutus. The mesozooplankton structure appears to be determined by available food resources and increased water temperature due to a strong influence of warm Atlantic waters.     

Seasonal variations in biomass, abundance and composition of zooplankton in the subarctic waters north of Iceland

The seasonal variations in biomass, abundance and species composition of zooplankton in relation to hydrography and chlorophyll a were studied in the subarctic waters north of Iceland. The sampling was carried out at approximately monthly intervals from February 1993 to February 1994 at eight stations arranged along a transect extending from 66°16′N–18°50′W to 68°00′N–18°50′W. The mean temperature at 50 m depth showed a clear seasonal pattern, with lowest water temperatures in February (∼1.1°C) and the highest in July (∼5.4°C). The spring growth of the phytoplankton began in late March and culminated during mid-April (∼7.0 mg Chl a m⁻³). Both the biomass and the abundance of total zooplankton were low during the winter and peaked once during the summer in late May (∼4 g m⁻² and ∼38,000 individuals m⁻²). A total of 42 species and taxonomic groups were identified in the samples. Eight taxa contributed ∼90% of the total zooplankton number. Of these Calanus finmarchicus was by far the most abundant species (∼60% of the total zooplankton). Less important groups were ophiuroid larvae (∼9%), Pseudocalanus spp. (∼8%), Metridia longa (∼4%), C. hyperboreus (∼3%), Acartia longiremis (∼2%), chaetognaths (∼2%) and euphausiid larvae (∼2%). The dominant copepods showed two main patterns in seasonal abundance: C. finmarchicus, C. hyperboreus and C. glacialis had one annual peak in numbers in late May, while Pseudocalanus spp., M. longa and A. longiremis showed two maxima during the summer (July) and autumn (October/November). Ophiuroid larvae and chaetognaths (mainly Sagitta elegans) peaked during the middle of July, while the number of euphausiid eggs and larvae was greatest from May to July. The succession in population structure of C. finmarchicus indicated its main spawning to be in April and May, coincident with the phytoplankton spring bloom. A minor spawning was also observed sometime between August and October. However, the offspring from this second spawning contributed only insignificantly to the overwintering stock of C. finmarchicus. Received: 12 September 1997 / Accepted: 1 March 1998     

Breaking the ice: large-scale distribution of mesozooplankton after a decade of Arctic and transpolar cruises

Mesozooplankton collected during five summer expeditions to the Arctic Ocean between 1987 and 1991 was analysed for regional patterns in biomass and species distribution, distinguishing between an epipelagic (0–100 m) and a deeper (0–500 m) layer. A total of 58 stations was sampled mainly in the Nansen, Amundsen and Makarov Basins of the central Arctic Ocean and in areas of the Greenland Sea, West Spitsbergen Current and Barents Sea. Results from the different expeditions were combined to create a transect extending from the Fram Strait across the Eurasian Basin into the Makarov Basin. Mesozooplankton dry mass in the upper 500 m decreased from 8.4 g m⁻² in the West Spitsbergen Current to less than 2 g m⁻² in the high-Arctic deep-sea basins. In the central Arctic Ocean, biomass was concentrated in the upper 100 m and was dominated by the large copepods Calanus hyperboreus and C. glacialis. In contrast, the mesozooplankton in the West Spitsbergen Current was more evenly distributed throughout the upper 500 m, with C. finmarchicus as the prevailing species. The distribution of abundant mesopelagic species reflected the hydrographic regime: the calanoid copepod Gaetanus tenuispinus and the hyperiid amphipod Themisto abyssorum were most abundant in the Atlantic inflow, while Scaphocalanus magnus was a typical component of the high-Arctic fauna. The relatively high mesozooplankton biomass and the occurrence of boreal-Atlantic species in the central Arctic Ocean are indicators for the import of organic material from allochthonous sources, especially from the northern North Atlantic. Hence, in spite of its enclosure by land masses, the Arctic Ocean is characterized by an exchange of water masses and organisms with the North Atlantic, and advection processes strongly influence the distribution of plankton species in this high-latitude ecosystem. Received: 18 December 1997 / Accepted: 11 April 1998     

Space-time variability of carbon standing stocks and fixation rates in the Gulf of Maine, along the GNATS transect between Portland, ME, USA, and Yarmouth, Nova Scotia, Canada

The Gulf of Maine North Atlantic Time Series has been run since1998 and is the longest transect time series in the Gulf ofMaine (GoM), USA. Here we use this coastal time series to documentthe space–time variability of hydrography, nutrients,phytoplankton standing stocks and carbon fixation in the GoM,in response to several years of extreme river discharge. Wehypothesize that, during wet years, fresh water input cappedthe surface euphotic layer, impeding the upward diffusion ofnutrients, thus lowering the phytoplankton biomass and carbonfixation rates. Regional algorithms were derived to estimateparticulate organic carbon and carbon fixation. The Howard–Yoderalgorithm was implemented to predict integral primary productionusing satellite ocean color data. Calcification was significantlycorrelated to primary production, thus allowing regional, satellite-derivedcalcification estimates. Total GoM and Georges Bank phytoplanktonphotosynthesis was 38.12 Tg C year^–1 and total calcificationwas 0.55 Tg C year^–1, yielding an overall ratio of calcificationto photosynthesis of 1.44%. Carbon fixation in GoM coastal water(<60 m bottom depth), GoM deep water (>60 m) and GeorgesBank waters (<60 m) averaged 33, 56 and 11% of the totalprimary production of the combined GoM and Georges Bank studyarea, respectively, and 22, 67 and 11% of the total calcificationof the study area, respectively.     

Seasonal and interannual variation of subtidal fish assemblages in Wakasa Bay with reference to the warming trend in the Sea of Japan

A bi-monthly underwater visual census was conducted in the subtidal habitat of Nagahama, Wakasa Bay, Sea of Japan, over 5 years from January 2002 to December 2006. A total of 83 fish species and 63,328 individuals were recorded over 120 1-h visual censuses composed of three 2 × 200 m transects. The number of both total individuals (abundance) and species (richness) were strongly correlated with the bottom-water temperature. Species richness was greatest in summer (July–September), with 10–20 species per 400 m², when the sea-bottom temperature was highest (24–28°C), and lowest in winter (January–March), with 1–8 species per 400 m², when the temperature was lowest (10–12°C). Five species, i.e., rockfish, Sebastes inermis, wrasse, Pseudolabrus sieboldi, two species of goby, Acentrogobius pflaumii and Tridentiger trigonocephalus, and pygmy filefish, Rudarius ercodes, were frequently observed and present in more than 200 of the total of 360 total transects. While the presence of most fish species was dependent on water temperature, some species were independent of water temperature, including anchovy, Engraulis japonicus, S. inermis, wasp fish, Hypodytes rubripinnis, A. pflaumii and pufferfish, Takifugu poecilonotus. Jack mackerel, Trachurus japonicus, was the most abundant fish, being most typically seen from spring through autumn, with a total of 21,850 individuals observed over the whole census period. Some species showed strong annual fluctuations in abundance. The interannual stability in fish abundance and species richness was probably because the fish assemblage was composed of a sufficiently large number of species, but with the number of each species fluctuating over time. A comparison of the present survey to one in 1970–72 revealed that over the last 30 years southern fish species have significantly increased whereas those indigenous to northern waters have decreased.

Hydrodynamic Control of Late Summer Species Composition and Abundance of Zooplankton in Hudson Bay and Hudson Strait (Canada)

The spatial variation in zooplankton biomass, abundance andspecies composition in relation to hydrography and chlorophylla (Chl a) was studied in the subarctic waters of Hudson Bayand Hudson Strait. Sampling was carried out in early September1993 at 21 stations arranged along a transect following theQuébec coast from James Bay, in Hudson Bay, to the vicinityof Ungava Bay in Hudson Strait. Both the biomass and the abundanceof total zooplankton were low along the lower part of HudsonBay (averaging 1.6 g DM m^–2 and 9432 ind. m^–2) andincreased sharply toward the upper end of the Bay and in HudsonStrait (averaging 6.0 g DM m^–2 and 40 583 ind. m^–2).A total of 80 zooplankton taxa was identified in the samples.Copepods were clearly numerically dominant at all sampling stations,accounting for more than 85% and 93% of the zooplankton communityin the Bay and the Strait, respectively. Clustering samplesby their relative species composition revealed four groups distributedalong well defined environmental gradients characterizing thedistribution of physical variables and Chl a. The first group,located in the most southern region of Hudson Bay and fartheroffshore, northwest of the Belcher and Sleeper Islands, wasstrongly influenced by freshwater run-off from James Bay andother major rivers around the Bay, and was characterized bythe presence of two euryhaline copepod species (Acartia longiremisand Centropages hamatus). The second and the third groups occupiedthe largest region along the sampling transect, from the middleof Hudson Bay to the western region of Hudson Strait, and werecharacterized by a typical arctic zooplankton fauna relatedto the cyclonic circulation in central Hudson Bay. The fourthgroup was located in the easternmost part of the sampling transectin Hudson Strait where the highest phytoplankton biomass valueswere observed (Chl a ~220 mg m^–2). The zooplankton assemblagethere showed an important increase in the abundance of the largeherbivorous copepod Calanus glacialis/finmarchicus, which werenumerically four times more abundant in the central Strait region(averaging 15 251 ind. m^–2) than in the western side ofHudson Strait and in Hudson Bay (3629 ind. m^–2). Theseresults support the hypothesis that the structure in the localbiological community is influenced by the local hydrodynamicfeatures which, through their action on surface water temperature,salinity, stratification and mixing conditions, lead to spatialdifferentiation of the phytoplankton and zooplankton communities.     

Temporal and spatial variation of dominant pelagic Copepoda (Crustacea) in the Weddell Sea (Southern Ocean) 1929 to 1993

The abundances of four dominant Antarctic copepod species, Metridia gerlachei, Rhincalanus gigas, Calanoides acutus and Calanus propinquus, were examined in the Southern Ocean in a combination of a literature review, analysis of museum samples and field sampling. The data were analysed for spatial and temporal variations. The data included in the analysis were from the Weddell Sea area in the summertime at periods 1929–1939 and 1989–1993. The results are discussed in the light of environmental changes and their hypothesised and observed consequences in the Southern Ocean: global temperature change, ozone deficiency and cascading trophic interactions. Combining all these hypothetical effects our null hypothesis was that there were no consistent long-term changes in the abundance of dominant pelagic Copepoda. The null hypothesis was rejected, since several taxons did show statistically significant long-term changes in abundance. The changes were not uniform however. The numbers of adults and juveniles of Calanus propinquus increased significantly between the periods studied. Adult stages of Calanoides acutus were the only taxon decreasing in abundance, in concert with the cascading trophic interactions theory. Latitudinally, only Metridia gerlachei showed a significant increase from north to south. Longitudinally, the abundances of Calanus propinquus juveniles and both adults and juveniles of Rhincalanus gigas increased from west to east. There were no significant variations between day and night samples. Interannual changes were statistically significant in juvenile stages of all the species and in adults of Calanus propinquus. We conclude that no uniform and consistent abundance changes could be observed in the pelagic Copepoda of the Weddell Sea that could be connected to major environmental changes, expected to affect the whole planktonic ecosystem of the Southern Ocean. Significant changes in some of the species studied show that the pelagic ecosystem is not in a steady state, but in addition to interannual changes, there are also major fluctuations extending over decades. Received: 5 December 1996 / Accepted: 24 March 1997     

Variation in liana abundance and biomass along an elevational gradient in the tropical Atlantic Forest (Brazil)

Lianas play a key role in forest structure, species diversity, as well as functional aspects of tropical forests. Although the study of lianas in the tropics has increased dramatically in recent years, basic information on liana communities for the Brazilian Atlantic Forest is still scarce. To understand general patterns of liana abundance and biomass along an elevational gradient (0–1,100 m asl) of coastal Atlantic Forest, we carried out a standard census for lianas ≥1 cm in five 1-ha plots distributed across different forest sites. On average, we found a twofold variation in liana abundance and biomass between lowland and other forest types. Large lianas (≥10 cm) accounted for 26–35% of total liana biomass at lower elevations, but they were not recorded in montane forests. Although the abundance of lianas displayed strong spatial structure at short distances, the present local forest structure played a minor role structuring liana communities at the scale of 0.01 ha. Compared to similar moist and wet Neotropical forests, lianas are slightly less abundant in the Atlantic Forest, but the total biomass is similar. Our study highlights two important points: (1) despite some studies have shown the importance of small-scale canopy disturbance and support availability, the spatial scale of the relationships between lianas and forest structure can vary greatly among tropical forests; (2) our results add to the evidence that past canopy disturbance levels and minimum temperature variation exert influence on the structure of liana communities in tropical moist forests, particularly along short and steep elevational gradients.     

福建中部近海浮游动物数量分布与水团变化的关系

根据2009—2010年在福建中部近海24°55'—25°13'N、119°11'—119°32'E水域冬、春、夏3个季节的调查资料,探讨了该水域浮游动物总丰度与生物量的平面分布、季节变化及其与台湾海峡水团变化的关系。结果表明,调查水域浮游动物的数量在冬、春之交变化较大,而在春、夏季变化较小。浮游动物冬、春两季的平均丰度分别为8.90 个/m³和245.65 个/m³,夏季为236.82 个/m³。冬、春两季,该水域浮游动物的分布特征相近。其数量在近岸较高,向外侧水域逐渐降低。冬季浮游动物的丰度最高为31.56 个/m³,春季最高达到831.67 个/m³。中华哲水蚤(Calanus sinicus)是冬、春季影响总丰度变化最主要的种类。与冬、春季不同,夏季浮游动物的数量在离岸水域较高,丰度最高达1053.13 个/m³,而在近岸较低,最低值仅19.17 个/m³。汉森莹虾(Lucifer hanseni)、双生水母(Diphyes chamissonis)是影响总丰度变化最主要的种类。浮游动物在各季的不同分布特征与台湾海峡的季节性水团变化有关。受季风转换影响,从冬季到夏季,海峡内沿岸流势力逐渐减弱,台湾暖流水势力逐渐增强,并影响到沿岸的水文环境。这导致调查水域内浮游动物的优势种类由暖温种向暖水种演替。由于冬、春季的重要优势种类中华哲水蚤与夏季的汉森莹虾、双生水母具有不同的温度适应性,受不同性质水团的影响,在近岸和离岸水域各自呈现出不同的数量高低。从而进一步影响到各季浮游动物总数量的分布。