Benthic Invertebrates in Delaware Bay: Animal-Sediment Associations of the Dominant Species

The purpose of this study was to determine the composition of the benthic fauna near the mouth of Delaware Bay. One hundred and five species were collected and identified from 277 grab samples. A sediment sample was also collected at each of the stations. Faunal density was low with the number of individuals rarely exceeding 10/0.1 m². Species were ranked according to number of individuals; the nine top species comprised 83.4% of the fauna. The top three species, Tellina agilis, Gemma gemma, and Nucula proxima, comprised 65.2% of all the individuals collected. A high percentage of the species (41.9%) occurred in two samples or less. The six most frequently collected species were compared with six sediment classes based on weight percentage of siltclay. Protohaustorius wigleyi and Trichophoxus epistomus were found mainly in less than 10% silt-clay. Tellina agilis and Ampelisca verrilli were transitional between the pure sand and mud facies. Nucula proxima and Heteromastus filiformis were members of a high silt-clay facies (<50% silt-clay). Diversity values were significantly greater (.05) in the low silt-clay sediments (0–25% silt-clay) than in the high silt-clay sediments (> 25% silt-clay). The relative dominance (redundancy) was not significantly different in any of the sediment types.     

Relationships between irradiance and photosynthesis for marine benthic green algae (Chlorophyta) of differing morphologies

Photosynthesis-irradiance relationships were determined in the field for five species of littoral and shallow sublittoral marine benthic green algae (Chlorophyta) of differing morphologies. Each species exhibited a linear increase in photosynthetic rate with increasing irradiance up to a maximum light-saturated value. Full sunlight (1405 to 1956 μE·m^?2·s^?1) inhibited photosynthesis of all species except the thick, optically dense, Codium fragile (Sur.) Har. Compensation irradiances ranged from 6.1 μE·m^?2·s^?1 for Enteromorpha intestinalis (L.) Link to 11.4 μE·m^?2·s^?1 for Ulva lobata (Kütz) S. & G. and did not reveal a consistent relationship to seaweed morphology. Saturation irradiances were determined statistically (I_k) and visually from graphical plots. with the latter technique resulting in values three to eight times higher and different comparative rankings of species than the former. I_k saturation irradiances were highest for Chaetomorpha linum (Müll.) Kütz. (81.9 μE·m^?2·s^?1) and lowest for Codium fragile (49.6 μE·m^?2·s^?1) and did not reveal a relationship with seaweed morphology. Regression equations describing light-limited photosynthetic rates and the relative magnitudes of the maximal net photosynthetic responses both strongly suggested a relationship with seaweed morphology. Highest net photosynthetic rates were obtained for the thin, sheet-like algae Ulva lobata (9.2 mg C·g dry wt^?1·h^?1), U. rigida C. Ag. (6.5 mg C·g dry wt^?1·h^?1) and the tubular form, Enteromorpha intestinalis (7.3 mg C·g dry wt^?1·h^?1), while lowest rates occurred for Codium fragile (0.9 mg C·g dry wt^?1·h^?1). Similarly, steepest light-limited slopes were found for the algae of simpler morphology, while the most gradual slope was determined for Codium fragile, the alga with greatest thallus complexity.     

The composition and distribution of benthic amphipods (Crustacea: Amphipoda) in the southern Barents Sea

The composition and distribution of near-bottom amphipods in the southern part of the central Barents Sea were studied based on quantitative materials collected by expeditions of the Murmansk Marine Biological Institute in 1996–1997. A total of 144 amphipod species (on average 13 ± 1 species per station) were found; the average biomass was 0.49 ± 0.07 g/m², average abundance 106 ± 15 specimens/m². Boreal-Arctic (46%), Arctic (17%), and boreal (21%) species were predominant among the amphipod fauna. The present results were compared with the data for 1968–1970.     

Standing fine root mass and production in four Chinese subtropical forests along a succession and species diversity gradient

Background and aims

The influences of succession and species diversity on fine root production are not well known in forests. This study aimed to investigate: (i) whether fine root biomass and production increased with successional stage and increasing tree species diversity; (ii) how forest type affected seasonal variation and regrowth of fine roots.

Methods

Sequential coring and ingrowth core methods were used to measure fine root production in four Chinese subtropical forests differing in successional stages and species diversity.

Results

Fine root biomass increased from 262 g·m^?2 to 626 g·m^?2 with increasing successional stage and species diversity. A similar trend was also found for fine root production, which increased from 86 to 114 g·m^?2 yr ^?1 for Cunninghamia lanceolata plantation to 211–240 g·m^?2 yr ^?1 for Choerospondias axillaries forest when estimated with sequential coring data. Fine root production calculated using the ingrowth core data ranged from 186 g·m^?2 yr ^?1 for C. lanceolata plantation to 513 g·m^?2 yr ^?1 for Lithocarpus glaber – Cyclobalanopsis glauca forest.

Conclusions

Fine root biomass and production increased along a successional gradient and increasing tree species diversity in subtropical forests. Fine roots in forests with higher species diversity exhibited higher seasonal variation and regrowth rate.     

Clearance rates of sessile rotifers: In situ determinations

Clearance rates of three sessile and four free-swimming rotifer species from a small acid bog-pond were measured using in situ techniques. Three radioactively labeled cell types, an alga (Chlamydomonas), a bacterium (Enterobacter = Aerobacter), and a yeast (Rhodotorula) were used as tracers. Clearance rates (using yeast) ranged from <1.0 to >250 µl · animal^?1 · h^?1 depending on species. Ptygura crystallina, Ptygura pilula, Floscularia conifera, and an unidentified bdelloid ingested all three foods with substantial variation in clearance rates among species and cell type. There was an insignificant error (<0.3%) in clearance rate associated with non-ingestive uptake of radioactivity. Among the free-swimming taxa, Lecane sp. had a clearance rate of <0.5 µl · animal^?1 · h^?1 on yeast, while another Lecane sp. and Trichotria tetractis did not ingest that cell type.     

TEMPERATURE AND IRRADIANCE EFFECTS ON GROWTH OF PITHOPHORA OEDOGONIA (CHLOROPHYCEAE) AND SPIROGYRA SP. (CHAROPHYCEAE)1

Growth responses of Pithophora oedogonia (Mont.) Wittr. and Spirogyra sp. to nine combinations of temperature (15°, 25°, and 35°C) and photon flux rate (50, 100, and 500 μmol·m^?2·s^?1) were determined using a three-factorial design. Maximum growth rates were measured at 35°C and 500 pmol·m^?2·s^?1 for P. oedogonia (0.247 d^?1) and 25°C and 500 μmol·m^?2·s^?1 for Spirogyra sp. (0.224 d^?1). Growth rates of P. oedogonia were strongly inhibited at 15°C (average decrease= 89%of maximum rate), indicating that this species is warm stenothermal. Growth rates of Spirogyra sp. were only moderately inhibited at 15° and 35°C (average decrease = 36 and 30%, respectively), suggesting that this species is eurythermal over the temperature range employed. Photon flux rate had a greater influence on growth of Spirogyra sp. (31% reduction at 50 pmol·m^?2·s^?1 and 25°C) than it did on growth of P. oedogonia (16% reduction at 50 μmol·m^?2·s^?1 and 35°C). Spirogyra sp. also exhibited much greater adjustments to its content of chlorophyll a (0.22–3.34 μg·mg fwt^?1) than did P. oedogonia (1.35–3.08 μg·mg fwt^?1). The chlorophyll a content of Spirogyra sp. increased in response to both reductions in photon flux rate and high temperatures (35°C). Observed species differences are discussed with respect to in situ patterns of seasonal abundance in Surrey Lake, Indiana, the effect of algal mat anatomy on the internal light environment, and the process of acclimation to changes in temperature and irradiance conditions.     

Caloric content of plant species and its role in a Leymus chinensis steppe community of Inner Mongolia, China

The caloric contents of 42 species and their composition in a Leymus chinensis steppe community of Inner Mongolia, China were determined and analyzed based on the field experiment for 11 years. The caloric content (x ± SD) of aboveground parts of plant species varied from (13156 ± 1141) J·g^?1 (ash contained) to (18141 ± 527) J·g^?1. The average caloric content of all species was (16899 ± 840) J·g^?1 and the inter-specific CV (coefficient of variation) was 4.9%. Of all the species, Caragana microphylla had the highest caloric content (18142 J·g^?1). Grasses had a higher average caloric content ((17425 ± 291) J·g^?1) than forbs ((16734 ± 844)J·g^?1). When the herbaceous species were classified into subgroups according to life-form and growth-form, the order of average caloric contents, from high to low, was: tall grasses ((17717 ± 92) J·g^?1) > legume ((17228 ± 433) J·g^?1) > short grasses ((17250 ± 218) J·g^?1) > remaining forbs ((16784 ± 529) J·g^?1) > subshrubs ((16719 ± 69) J·g^?1) > annuals and biennials ((15911 ± 1759) J·g^?1). There was a positive correlation (P < 0.05) between the caloric contents of 42 species and their relative biomass in the community. When all species were classified into 3 groups according to their composition in the community, the average caloric contents, weighed by the species relative biomass, followed the order: dominant (17740 J·g^?1) > companion (17244 J·g^?1) > incidental (16653 J·g^?1). The plants with high caloric contents were more competitive, which allowed them to gain a dominant status, whereas the competitive abilities of plants with low caloric contents were generally weak. The latter made up the companion or incidental species in a steppe community.     

Biomass and Lipid Production of Dinoflagellates and Raphidophytes in Indoor and Outdoor Photobioreactors

The principal fatty acids from the lipid profiles of two autochthonous dinoflagellates (Alexandrium minutum and Karlodinium veneficum) and one raphidophyte (Heterosigma akashiwo) maintained in bubble column photobioreactors under outdoor culture conditions are described for the first time. The biomass production, lipid content and lipid productivity of these three species were determined and the results compared to those obtained when the strains were cultured indoors. Under the latter condition, the biotic values did not significantly differ among species, whereas under outdoor conditions, differences in both duplication time and fatty acids content were observed. Specifically, A. minutum had higher biomass productivity (0.35 g·L^?1 day^?1), lipid productivity (80.7 mg lipid·L^?1 day^?1) and lipid concentration (252 mg lipid·L^?1) at harvest time (stationary phase) in outdoor conditions. In all three strains, the growth rate and physiological response to the light and temperature fluctuations of outdoor conditions greatly impacted the production parameters. Nonetheless, the species could be successfully grown in an outdoor photobioreactor and were of sufficient robustness to enable the establishment of long-term cultures yielding consistent biomass and lipid production.     

Foliar maintenance respiration of subalpine and boreal trees and shrubs in relation to nitrogen content

A nitrogen-based model of maintenance respiration (R_m) would link R_m with nitrogen-based photosynthesis models and enable simpler estimation of dark respiration flux from forest canopies. To test whether an N-based model of R_m would apply generally to foliage of boreal and subalpine woody plants, I measured R_m (CO₂ efflux at night from fully expanded foliage) for foliage of seven species of trees and shrubs in the northern boreal forest (near Thompson, Manitoba, Canada) and seven species in the subalpine montane forest (near Fraser, Colorado, USA). At 10°C, average R_m for boreal foliage ranged from 0.94 to 6.8μmol kg^?1 s^?1 (0.18–0.58 μmol m^?2 s^?1) and for subalpine foliage it ranged from 0.99 to 7.6 μmol kg^?1 s^?1 (0.28–0.64μmol m^?2 s^?1). CO₂ efflux at 10°C for the samples was only weakly correlated with sample weight (r = 0.11) and leaf area (r = 0.58). However, CO₂ efflux per unit foliage weight was highly correlated with foliage N concentration [r = 0.83, CO₂ flux at 10°C (mol kg^?1 s^?1) = 2.62 × foliage N (mol kg^?1)J, and slopes were statistically similar for the boreal and subalpine sites (P=0.28). CO₂ efflux per unit of foliar N was 1.8 times that reported for a variety of crop and wildland species growing in warmer climates.     

Biphasic regulation of superoxide radical levels in Mn-depleted and photoactivated photosystem II

In the past decades, it has become clear that superoxide radical (O₂ ^·?) can be generated from photosystem II (PSII) during photosynthesis. Depending on the extent of its accumulation, O₂ ^·? plays an important role in plant physiology and pathology. The photoinhibition/repair cycle is a typical process in PSII which is mainly responsible for the survival of plants under the photoinihibition condition. It is therefore of significant importance to determine O₂ ^·? production in this cycle, and then explore how O₂ ^·? is controlled by PSII within a normal physiological level. With this in mind, we herein investigate the variation of the O₂ ^·? levels in PSII under Mn-depleted and photoactivated conditions mimicking the photoinhibition/repair cycle in vitro. The effect of intrinsic SOD-like component on the O₂ ^·? levels was also studied. Results show that PSII has the ability to regulate the O₂ ^·? levels in these two processes by simultaneously modulating the O₂ ^·? generation activity and intrinsic SOD-like activity. This finding could shed new lights on the photoprotective property of PSII against O₂ ^·? and other reactive oxygen species.     

Photosynthesis and respiration in a fast growing strain of Gigartina exasperata (Harvey and Bailey)

Photosynthesis and respiration rates of blades from a selected, fast growing strain of the marine red alga. Gigartina exasperata Harvey and Bailey, a carrageenan producer, were measured with an oxygen electrode and compared with rates similarly obtained from wild material of the same species. The measurements, expressed as μl O₂ · mg chl a^?1, min^?1. were made over a light intensity range from 5 to 800 μE · m^?2 · sec^?1 and a temperature range of 6 to 16°C. The photosynthesis light intensity data are best described by hyperbolic functions.     

Composition,abundance and distribution of holoplanktonic polychaetes within the Strait of Magellan (southern America) in austral summer

This study enlarge the knowledge on species composition, distribution and community structure of pelagic polychaetes on the basis of finely stratified spatial sampling representing austral summer conditions in the Strait of Magellan. Zooplankton samples were collected in late austral summer 1995. A total of 56,489 pelagic polychaete specimens were collected. Eight holopelagic polychaete taxa were recorded in addition to Spionidae and Terebellidae larvae and reproductive stolons of Autolytinae. Pelagobia longicirrata (Lopadorhynchidae) was the most abundant species, representing about 96 % (54,092 specimens, 184.6 ind. 100 m^?3) of all individuals, followed by Tomopteris planktonis (Tomopteridae) at 3 % (1,725 specimens, 5.9 ind. 100 m^?3). The longest measured individuals belonged to T. planktonis, which also showed the largest size range, whereas the smallest individuals belonged to P. longicirrata. Spatial distribution of polychaetes in terms of abundance was not related to bottom depth, but rather the number of taxa was lower in the central part of the Strait. P. longicirrata and T. planktonis were negatively related to chlorophyll a. In addition, the first was negatively related to temperature instead the second was positively affected by salinity. Polychaetes were widely distributed in both epi- and mesopelagic realms, whereas they were almost absent above 80 m depth. Both of the most abundant species were concentrated in the deepest layers sampled (below 100 m) throughout day and night hours without showing any specific migratory behavior.     

Interactions between gnathiid isopods,cleaner fish and other fishes on Lizard Island,Great Barrier Reef

The rate of emergence of micropredatory gnathiid isopods from the benthos, the proportion of emerging gnathiids potentially eaten by Labroides dimidiatus, and the volume of blood that gnathiids potentially remove from fishes (using gnathiid gut volume) were determined. The abundance (mean ±s.e .) of emerging gnathiids was 41·7 ± 6·9 m^?2 day^?1 and 4552 ± 2632 reef^?1 day^?1 (reefs 91–125 m²). The abundance of emerging gnathiids per fish on the reef was 4·9 ± 0·8 day^?1; but excluding the rarely infested pomacentrid fishes, it was 20·9 ± 3·8 day^?1. The abundance of emerging gnathiids per patch reef was 66 ± 17% of the number of gnathiids that all adult L. dimidiatus per reef eat daily while engaged in cleaning behaviour. If all infesting gnathiids subsequently fed on fish blood, their total gut volume per reef area would be 17·4 ± 5·6 mm³ m^?2 day^?1; and per fish on the reefs, it would be 2·3 ± 0·5 mm^?3 fish^?1 day^?1 and 10·3 ± 3·1 mm³ fish^?1 day^?1 (excluding pomacentrids). The total gut volume of gnathiids infesting caged (137 mm standard length, L_S) and removed from wild (100–150 mm L_S) Hemigymnus melapterus by L. dimidiatus was 26·4 ± 24·6 mm³ day^?1 and 53·0 ± 9·6 mm³ day^?1, respectively. Using H. melapterus (137 mm L_S, 83 g) as a model, gnathiids had the potential to remove, 0·07, 0·32, 0·82 and 1·63% of the total blood volume per day of each fish, excluding pomacentrids, caged H. melapterus and wild H. melapterus, respectively. In contrast, emerging gnathiids had the potential of removing 155% of the total blood volume of Acanthochromis polyacanthus (10·7 mm L_S, 0·038 g) juveniles. That L. dimidiatus eat more gnathiids per reef daily than were sampled with emergence traps suggests that cleaner fishes are an important source of mortality for gnathiids. Although the proportion of the total blood volume of fishes potentially removed by blood‐feeding gnathiids on a daily basis appeared to be low for fishes weighing 83 g, the cumulative effects of repeated infections on the health of such fish remains unknown; attacks on small juvenile fishes, may result in possibly lethal levels of blood loss.     

A tradeoff between space and time: Dimensional constants in mammalian ecology

Size-independent dimensional constants are proposed as a tool for analysis of life histories and community structure. The number of conspecific individuals occupying the average home-range in the long-run is 2·15 M^?0·02, accomplished sequentially or socially at opposite ends of the mouse to wapiti body size range. Annual biomass turnover per species per hectare is also independent of body size, 0·93 N^?0·04.     

Migrant shorebird use of Akimiski Island, Nunavut: a sub-arctic staging site

Determining the importance of stopover and staging areas to migrating shorebirds (Aves: Charadriiformes) is essential if such habitats are to be successfully protected. Migration chronology, species composition, length of stay, body condition, and estimated total abundance of shorebirds during spring and fall migratory periods of 2008 and 2009 were documented on Akimiski Island, Nunavut, Canada. Fourteen shorebird species were observed during spring point counts and 18 during fall. Semipalmated (Calidris pusilla) and White-rumped (C. fuscicollis) Sandpipers comprised about 80?% of all individuals observed. A greater number of species and individuals were observed during fall than spring in both years. Radio-transmitters attached to juvenile Semipalmated and Least (C. minutilla) Sandpipers indicated highly variable lengths of stay ranging up to 26?days in both species (Semipalmated Sandpiper averaged 6.5?±?2.67?days, n?=?12; Least Sandpipers averaged 7.25?±?3.79?days, n?=?8). In 2009, Semipalmated Sandpipers captured and weighed later in the season were significantly heavier than those captured earlier suggesting that this species is refueling while on Akimiski Island. A fall migration seasonal density of 5,267 (2,193–8,341) shorebirds/km² was estimated given a residence probability (i.e., the probability of an individual being present in consecutive counts) of 0.906?±?0.181. Assuming similar habitat value and shorebird density, an extrapolation of the seasonal plot density of 5,267 birds/km² to the total 192?km² mudflat habitat on Akimiski Island yields an estimate of 1,011,264 (421,098–1,601,429) shorebirds during fall migration, making Akimiski Island of Hemispheric importance as a staging site for migrant arctic-breeding shorebirds.     

Skeletal growth in the echinoderm Asterias rubens L. (Asteroidea,Echinodermata) estimated by 45Ca-labelling

The skeletal dry weight of the 4.4 ± 0.2 cm size class of Asterias rubens L. from Kiel Bay in the western Baltic is 0.34 ± 0.08 g. The sum of calcium and magnesium carbonates in the skeleton amounts to 94.0 ± 1.3% while the individual concentrations are 86.9 ± 1.3% CaCO₃ and 7.1 ± 0.7% MgCO₃. The MgCO₃ is 4% lower than expected for a magnesium calcite precipitated under Baltic temperature conditions (8°C). Strontium was not determined but strontium carbonate is known to be in the region of 0.4%. The remainder is organic matter and this gives rise to 2.9 ± 1.3% organic carbon.Animals studied were at the ‘waiting stage’ and their actual growth was minimal. Uptake of ⁴⁵Ca in the skeleton consists of a fast step followed by a slow step. The fast step is attributed to saturation of exchangeable skeletal pools while the slow step is due to net deposition of CaCO₃. Skeletal growth at the waiting stage calculated from the second rate constant was found to be 0.76 μg CaCO₃j-mg skeleton^?1 · day^?1 or 0.09% · day^?1 compared with 9.3 μg CaCO₃ · mg skeleton^t1&#x0304; · day^?1 or 1.1% · day^?1 at log phase. The isotope method is considered superior to size-frequency analysis in that it is capable of detecting differences in growth rate in individuals of the same size class and thus provides an insight into asteroid population structure.     

Meiofauna and macrofauna communities in a mangrove from the Island of Santa Catarina, South Brazil

The composition and abundance of the meiofauna and macrofauna were studied in a survey carried out within 6 locations in a mangrove at the Island of Santa Catarina, South Brazil. Nine meiofaunal taxa were registered with densities ranging between 77 and 1589 inds.10 cm^?2. The nematodes, composed by 94 putative species (86 genera), largely dominated the meiofauna. The most abundant genera were Haliplectus (Haliplectidae), Anoplostoma (Anoplostomatidae) and Terschillingia (Linhomoidae). Contrary to the meiofauna, the macrofauna showed a low number of taxa (only 17 recorded) and abundance (up 7250 inds.m^?2). The macrofauna was mainly composed by deposit feeders, and numerically dominated by oligochaetes and capitellid polychaetes. For both components, differences in the composition and abundance along the sampling sites were significant but not primarily related to the typical variations along estuaries, such as salinity. The results of the stepwise multiple regression analyses showed that the detritus biomass (ash-free dry weight) was the most important predictor of faunal densities and diversity. The clear relationship between detritus and fauna, together with the contrasting community structure of the two component of the benthos suggest that the meiofauna showed a high efficiency in exploiting the micro-habitat created by the presence of the detritus. Yet the macrofauna, potentially the main consumer of the debris, is negatively affected by their low palatability and poor nutritive value.     

Microphytobenthic species composition,pigment concentration,and primary production in sublittoral sediments of the Trondheimsfjord (Norway)1

In spring 2005, monthly sampling was carried out at a sublittoral site near Tautra Island. Microphytobenthic identification, abundance (ABU), and biomass (BIOM), were performed by microscopic analyses. Bacillariophyceae accounted for 67% of the total ABU, and phytoflagellates constituted 30%. The diatom floristic list consisted of 38 genera and 94 species. Intact light‐harvesting pigments chl a, chl c, and fucoxanthin and their derivatives were identified and quantified by HPLC. Photoprotective carotenoids were also observed (only as diadinoxanthin; no diatoxanthin was detected). Average fucoxanthin content was 4.57 ± 0.45 μg fucoxanthin · g sediment dry mass^?1, while the mean chl a concentration was 2.48 ± 0.15 μg · g^?1 dry mass. Both the high fucoxanthin:chl a ratio (considering nondegraded forms) and low amounts of photoprotective carotenoids indicated that the benthic microalgal community was adapted to low light. Microphytobenthic primary production was estimated in situ (MPPs, from 0.15 to 1.28 mg C · m^?2 · h^?1) and in the laboratory (MPPp, from 6.79 to 34.70 mg C · m^?2 · h^?1 under light saturation) as ¹⁴C assimilation; in April it was additionally estimated from O₂‐microelectrode studies (MPP_O2) along with the community respiration. MPP_O2 and the community respiration equaled 22.9 ± 7.0 and 7.4 ± 1.8 mg C · m^?2 · h^?1, respectively. A doubling of BIOM from April to June in parallel with a decreasing photosynthetic activity per unit chl a led us to suggest that the microphytobenthic community was sustained by heterotrophic metabolism during this period.     

Distribution patterns of micro- and meso-zooplankton communities in sea ice regions of Lützow-Holm Bay, East Antarctica

In the Southern Ocean, zooplankton research has focused on krill and macro-zooplankton despite the high densities of micro- and meso-zooplankton. We investigated their community structure in relation to different sea ice conditions around Japan’s Syowa Station in Lützow-Holm Bay, in the summers of 2011 and 2012. Zooplankton samples were collected using vertical hauls (0–150 m), with a closing net of 100-μm mesh size. The results of cluster analysis showed that the communities in this region were separated into fast ice, pack ice, and open ocean fauna. The fast ice fauna had lower zooplankton abundance (393.8–958.9 inds. m^?3) and was dominated by cyclopoid copepods of Oncaea spp. (54.9–74.8 %) and Oithona similis (6.6–19.9 %). Deep-water calanoid copepods were also found at the fast ice stations. Pack ice and open ocean fauna had higher zooplankton abundance (943.6–2,639.8 inds. m^?3) and were characterized by a high density of foraminiferans in both years (6.6–61.9 %). Their test size distribution indicated that these organisms were possibly released from melting sea ice. The pteropod Limacina spp. was a major contributor to total abundance of zooplankton in the open ocean zone in 2012 (26.4 %). The physical and/or biological changes between 2 years may affect the abundance and distribution of the dominant zooplankton taxa such as cyclopoid copepods, foraminiferans, and pteropods. Information on the relationships between the different species associated with sea ice will help to infer the possible future impacts of climate change on the sea ice regions.