Spawning patterns of four species of predominantly temperate pelagic fishes in the sub-tropical waters of southern Queensland

The diverse pelagic fish assemblage of sub-tropical southern Queensland includes fishes with predominantly temperate distributions, such as tailor Pomatomus saltatrix, sardine Sardinops sagax, round herring Etrumeus teres, and Australian anchovy Engraulis australis. The peak spawning seasons of P. saltatrix, S. sagax and E. teres occur during late winter and early spring (June–October). Eggs and larvae of these three species are widely distributed in shelf waters and comprise >50% of the ichthyoplankton assemblage during this period. Mean monthly sea surface temperatures (SSTs) during late winter and early spring range from 21 to 23 °C, and are thus similar to those recorded in southern Australia during summer and autumn, which is the spawning season of these three species in those temperate waters. E. australis eggs occur mainly in inshore waters, and comprise >50% of fish eggs collected during summer and autumn when mean monthly SSTs in southern Queensland exceed 27 °C. E. australis also spawns mainly during summer and autumn in temperate Australia. Hence, water temperature may be less important as a determinant of the spawning season of E. australis than it is for the other three species. The suitability of southern Queensland for spawning by predominantly temperate species during late winter and early spring may contribute to the high diversity of the region's pelagic fish assemblage. Adult P. saltatrix, S. sagax and E. teres appear to migrate northwards into southern Queensland during early winter to spawn, and larvae may be transported southwards into temperate waters by the East Australian Current. This dispersal-migration pattern is similar to those observed for several species, including P. saltatrix, in the western boundary current systems off the east coasts of North America and Africa. Hence, pelagic fishes in ecosystems off the east coast of three continents migrate into sub-tropical waters to spawn, and larvae are transported back into temperate nursery areas by the prevailing current.     

Growth, Production, and a Partial Energy Budget for the Amphipod, Talorchestia capensis (Crustacea; Talitridae) in the Eastern Cape, South Africa

Abstract. .A population of Talorchestia capensis was sampled in dune slacks over the period of one year. Two hatching periods, one in March and one in September, were observed. Growth was rapid, the amphipods reaching a size of 8.4 mm standard length in 18 months. Maximum growth occurred in spring and minimum growth in winter. Annual mortality rates for summer- and winter-hatched individuals were low, 0.22-y“¹ and 0.16-y”¹. Average production for the summer classes was 7.2g-y?‘ (dry mass) and for the winter classes 2.9-y“¹, with a P/B ratio of 2.25-y”’. Production values peaked during autumn and summer. Abundance and biomass estimates showed maxima during summer and minima in early spring. Reproductive output was low, 0.1 kJ ? m^-2 y“¹, indicating that 7 % of the total production is used for reproduction and 93 % for somatic production. The assimilated energy flow through the population was estimated to be 16.3 kJ m?² y?‘ and consumption about 81.6 kJ m^-2 y^_’.     

The response of primary producer assemblages to mitigation measures to reduce eutrophication in a temperate estuary

The Mondego estuary is a well-described system located on the North Atlantic Ocean, where cultural eutrophication progressed over the last decades of the 20th century. Consequently, and due to a large productivity of Ulva spp., Zostera noltii meadows were severely reduced with a concomitant decrease in environmental quality. In 1998, experimental mitigation measures were implemented, via changes in hydrology to increase circulation and diversion of nutrient-rich freshwater inflow, to reverse the process in the most affected area of the estuary – its South arm.The objective of this study was to assess the differences in response of primary producer assemblages to the implemented measures to reduce eutrophication.Results show that the mean concentrations of DIN suffered a notorious decrease due to a significant reduction in the ammonium concentration in the water column, while DIP increased significantly. Primary producer assemblages showed different responses to these changes: phytoplankton, measured as concentration of chlorophyll a, did not show any significant changes; green macroalgae, mostly Ulva spp., suffered a large reduction in biomass, whereas Gracilaria gracilis and the macrophyte Zostera noltii biomasses increased greatly. Results show that phytoplankton biomass has remained constant and suggest that the reduction in ammonium could have been responsible for the changes in the green macroalgal biomass. Light was the most likely factor in the response of seagrass whereas red macroalgal reaction seemed to be dependent on both light and ammonium.     

Seasonal succession of cyanoprokaryotes in a hypereutrophic oligo-mesohaline lagoon from the South of France

The Bolmon lagoon (South of France) is an oligo-mesohaline coastal lagoon that has undergone intense eutrophication in the past decades, resulting from a strong concentration of human activities in its drainage basin. Consequently, it exhibits some characteristics typical of an advanced trophic state; namely, the disappearance of submerged vegetation, the permanently intense phytoplankton growth and the recurrence of cyanoprokaryote blooms. As cyanoprokaryote dominance in south-temperate saline lagoons is little reported, we carried out this study in order to understand the seasonal variations in the phytoplankton composition and biomass, and to analyse the influence of environmental parameters such as salinity, nutrients and climate on the seasonal succession of species. In this lagoon, the phytoplankton was permanently dominated by cyanoprokaryotes, probably because of high availability of nutrients, low light penetration in the water column and frequent turbulent mixing induced by wind. The two most abundant species Planktothrix agardhii (in winter–spring) and Pseudanabaena limnetica (in summer) have low light requirements and are well adapted to a high mixing frequency, which defines the S1 functional group in Reynolds' typology for phytoplankton. Although widely studied in north-temperate lakes, blooms of these typically freshwater species are almost unreported in the Mediterranean area, especially in brackish ecosystems that are not their normal habitat. In the Bolmon lagoon, all their requirements for nutrients, light and mixing are satisfied and they seem to cope with a moderate presence of salt but P. agardhii was less competitive than P. limnetica at highest salinities, the latter being probably more halophytic. Contrary to the observations in lakes located at higher latitudes, the Mediterranean climate seems to induce a typical seasonal pattern of succession characterised by the dominance of P. agardhii (winter) – Chroococcales (spring) – Pseudanabaenaceae (summer) – P. agardhii (autumn, winter). The warm temperatures seemed to have a major influence on the phytoplankton succession, being responsible for the survival of Planktothrix during winter and its rapid and intense development in early spring. Intense mixing and high irradiance in summer promoted the development of Pseudanabaenaceae, as reported in another south-temperate lagoon, the Albufera of Valencia (Spain). The ecological success of Oscillatoriales observed in the Bolmon lagoon is a perfect example of a shift to the “turbid stable state” as proposed for freshwater shallow lakes only. Our work demonstrated that hypereutrophic Mediterranean lagoons can function very similarly to shallow lakes at higher latitudes; but the warmer climate and higher irradiances are probably responsible for differences in the seasonal pattern of species dominance.     

2009-2018年南黄海苏北浅滩海域漂浮浒苔和马尾藻现场调查研究

利用2009-2018年在南黄海苏北浅滩海域的现场调查数据,分析和研究了该海域漂浮绿藻和马尾藻的长期变化和季节性波动特征。研究显示,漂浮绿藻于每年4月中旬至下旬在浅滩中部筏架周围开始出现。5月－6月,漂浮绿藻生物量迅速增加,并漂移扩散至深水区。漂浮绿藻密度年际变化较大,但这十年间总体呈上升趋势。相比较而言,漂浮马尾藻仅在2013、2017和2018年在浅滩聚集形成春季藻华;且这三年,漂浮马尾藻密度超过同期漂浮绿藻。浅滩漂浮马尾藻的发生与发展过程与漂浮浒苔明显不同。3月,漂浮马尾藻开始出现于浅滩离岸海域,4-5月,漂浮马尾藻大量侵入浅滩,因此浅滩漂浮马尾藻现并非起源于本地。受高强度人类活动以及浅滩以外海域物理化学和生物过程的影响,浅滩环境因素与漂浮绿藻生物量的关系不甚明确。对于漂浮马尾藻的起源以及与漂浮绿藻的相互关系也需要进一步研究。     

Diet composition and resource partitioning in two small flatfish species in the German Bight

Since the late 1980s, the small-sized non-commercial flatfish species solenette (Buglossidium luteum) and scaldfish (Arnoglossus laterna) have increased in abundance in the southern North Sea. Because these species are considered as possible competitors for prey of commercial flatfish, this study aimed at advancing knowledge of their feeding ecology.Between January 2009 and January 2010 stomach contents of solenette and scaldfish and benthic infauna were sampled seasonally in a study area in the German Bight. The objectives were to investigate the seasonal variability of feeding activity and diet composition of both flatfish species related to benthic prey availability.For both flatfish, the highest feeding activity was found in summer, at the same time that the highest prey densities occurred in the study area. A reduced feeding activity was observed during the winter of 2010, but not in the winter of 2009, probably related to higher 2009 water temperatures.In all seasons, diet composition of solenette was dominated by meiofauna, mainly harpacticoid copepods. Macrofauna prey species, namely juveniles of bivalves and echinoderms became important in spring. An increase in amphipods and cumaceans was found in the stomach contents during summer and autumn, simultaneously with their increased abundance in the benthic infauna. In contrast, polychaetes were rarely found in the diet, but dominated the infauna during all seasons.Diet composition of scaldfish was dominated by larger and mobile prey, and, during all seasons, was mainly comprised of crustaceans. Amphipods characterised the diet in both winters, while decapods such as Crangon spp. and Liocarcinus spp. were the dominant prey from spring to autumn. Additionally, juveniles of flatfish (Pleuronectids) and bivalves were found in the scaldfish diet in spring, replaced by cumaceans in summer. No dietary overlap between both flatfish species was found across seasons, indicating partitioning of prey resources between solenette and scaldfish. Their different feeding strategies and prey preferences, in turn were influenced by the seasonal variability of available prey.     

Recruitment of flatfish species to an estuarine nursery habitat (Lima estuary, NW Iberian Peninsula)

One of the present concerns of fish biologists involves defining and identifying nursery habitats in the context of conservation and resource management strategies. Fish nursery studies usually report upon nursery occupation during the latter juvenile stages, despite the fact that recruitment to nurseries can start early in life, during the larval phase. Here we investigated the use of a temperate estuarine nursery area, the Lima estuary (NW Portugal), by initial development stages of flatfish species before and after metamorphosis, integrating the larval and juvenile phases. The Lima estuarine flatfish community comprised twelve taxa, seven of which were present as pelagic larvae, six as juveniles and three as adults. There was a general trend of increasing spring–summer abundance of both larvae and juveniles, followed by a sharp winter decrease, mainly of larval flatfishes. The Lima estuary was used by Solea senegalensis, Platichthys flesus and Solea solea as a nursery area, with direct settlement for the two first species. In contrast, indirect settlement was suggested for S. solea, with metamorphosis occurring outside the estuarine area. Estuarine recruitment of S. senegalensis varied between years, with young larvae occurring in the estuary throughout a prolonged period that lasted 6–9 months, corroborating the protracted spawning season. P. flesus, the second most abundant species, exhibited a typical spring estuarine recruitment, without inter-annual variations. Developed larvae arrived in the estuary during spring, whereas the 0-group juveniles emerged in the following summer period. The present study contributes new insight to our understanding of the economically important S. senegalensis, and highlights the importance of integrating the planktonic larval phase into traditional flatfish nursery studies.     

Environmental controls on phytoplankton community composition in the Thames plume, U.K.

The aim of this study was to investigate controls on the phytoplankton community composition and biogeochemistry of the estuarine plume zone of the River Thames, U.K. using an instrumented moored buoy for in situ measurements and preserved sample collection, and laboratory-based measurements from samples collected at the same site. Instrumentation on the moored buoy enabled high frequency measurements of a suite of environmental variables including in situ chlorophyll, water-column integrated irradiance, macronutrients throughout an annual cycle for 2001 e.g. nitrate and silicate, and phytoplankton biomass and species composition. The Thames plume region acts as a conduit for fluvial nutrients into the wider southern North Sea with typical winter concentrations of 45 μM nitrate, 17 μM silicate and 2 μM phosphate measured. The spring bloom resulted from water-column integrated irradiance increasing above 60 W h m^− 2 d^− 1 and was initially dominated by a diatom bloom mainly composed of Nitzschia sp. and Odontella sinesis. The spring bloom then switched after  30 days to become dominated by the flagellate Phaeocystis reaching a maximum chlorophyll concentration of 37.8 μg L^− 1. During the spring bloom there were high numbers of the heterotrophic dinoflagellates Gyrodinium spirale and Katodinium glaucum that potentially grazed the phytoplankton bloom. This diatom–flagellate switch was predicted to be due to a combination of further increasing water-column integrated irradiance > 100 W h m^− 2 d^− 1 and/or silicate reaching potentially limiting concentrations (< 1 μM). Post spring bloom, diatom dominance of the lower continuous summer phytoplankton biomass occurred despite the low silicate concentrations (Av. 0.7 μM from June–August). Summer diatom dominance, generally due to Guinardia delicatula, was expected to be as a result of microzooplankton grazing, dominated by the heterotrophic dinoflagellate Noctiluca scintillans, controlling 0.7–5.0 μm ‘flagellate’ fraction of the phytoplankton community with grazing rates up to 178% of ‘flagellate’ growth rate. The Thames plume region was therefore shown to be an active region of nutrient and phytoplankton processing and transport to the southern North Sea. The use of a combination of moorings and ship-based sampling was essential in understanding the factors influencing nutrient transport, phytoplankton biomass and species composition in this shelf sea plume region.     

Seasonal abundance and reproductive strategy of Tetrastemma fozensis (Hoplonemertea, Nemertea) in the Villaviciosa estuary (Asturias, Northern Spain)

The seasonal occurrence and reproductive strategy of the nemertean Tetrastemma fozensis, which inhabits the mantle cavity of the bivalve Scrobicularia plana, was studied through the analysis of the temporal diversity of a T. fozensis population. Bimonthly sampling was carried out from February 2001 to January 2002 at mudflats of Villaviciosa estuary (Asturias, Northern Spain). Nemerteans were found throughout the study period, but variations in their abundance were detected, with a maximum during winter months and a minimum during summer months. Moreover, variations in mean size of nemerteans were found, with maximal sizes at the end of the spring and the beginning of the summer and minimum size at early autumn. The annual variations in population parameters (decrease in abundance and complete disappearance of large individuals in summer) suggest that T. fozensis has a distinct reproductive season and a semelparous reproductive strategy.     

Colonization process by macrobenthic infauna after a managed coastal realignment in the Bidasoa estuary (Bay of Biscay, NE Atlantic)

The colonization process by macrobenthic infauna after the completion of managed realignment on the fertile plain of Jaitzubia, along the Bidasoa estuary, is assessed here. The benthic invertebrate fauna was sampled annually for three years in the newly recovered intertidal areas. The results show a rapid colonization process. Six months after the completion of the restoration works, all the stations exhibited a large number of small opportunistic benthic species, as well as some large individuals of Hediste diversicolor, that dominated the biomass of the community. One year later, a new stage of development or succession towards the settlement of the Scrobicularia plana–Cerastoderma edule community was observed, showing a reduction of both abundance and species richness, and an increase in biomass, mainly due to the presence of individuals of S. plana (which were absent previously). The following year, a further reduction in the abundance and number of species was observed, as well as an increase in biomass, but on this occasion S. plana was the main contributor to community biomass. Evidence of the importance of passive or active dispersion in the adult stage of the species H. diversicolor and S. plana in the recovery process was also observed.     

海州湾前三岛海域底播刺参群体特征初探

海州湾前三岛海域是中国刺参(Apostichopus japonicus)自然分布的最南界,2013年3月至2014年4月,采用潜水样带法,调查了前三岛海域底播刺参群体的体质量结构及季节变动特征,结合水下观察和视频调查,比较了不同生境类型中的刺参密度。结果表明,前三岛海域刺参密度为0.4~1.33头/m2,生物量为42.69~103 g/m2,刺参群体相对稳定,群体的体质量呈现冬春季节增长、夏秋季节下降的特点。不同生境类型中的刺参密度不同,大型藻类分布的礁石区刺参密度明显大于没有藻类分布的礁石区和砂质区,上述结果为揭示岛屿海域的刺参群体特征和资源养护提供了基础数据。     

两株硅藻筒柱藻和纤细角毛藻的油脂生产

通过气泡柱光反应器评价了两株硅藻筒柱藻(Cylindrotheca fusiformis)和纤细角毛藻(Chaetoceros gracilis)的生物量、油脂及甘油三脂的积累.结果发现,其生物量与油脂产率相当,脂肪酸组成方面,也均以C16:0和C16:1为主,但是筒柱藻的油脂组成以甘油三酯为主,纤细角毛藻的油脂以单酰甘油酯、磷脂和糖脂为主.通过培养条件的优化,发现相比于降低初始氮元素与硅元素,降低培养液盐度,能够获得更高的生物量、油脂以及甘油三脂产率.通过筒柱藻批次培养最高获得了0.36 g/(L·d)的甘油三脂产率,且甘三酯占收获干物质的50%以上,具有相当好的应用潜力.     

冬夏季南海西部固氮蓝藻

本研究分析了冬季东北季风期(2006年11月27日-12月16日)及夏季西南季风期(2007年8月11日-9月16日)南海西部越南沿岸区域(10°~17°N,108°~115°E)的网采浮游植物样品,探讨了冬夏两季南海西部固氮蓝藻的物种、丰度及分布特征,以及影响固氮蓝藻丰度与分布的环境因素。冬夏两季南海西部固氮蓝藻主要有束毛藻(Trichodesmium)和胞内植生藻(Richelia intracellularis),束毛藻物种包括铁氏束毛藻(Trichodesmium thiebaultii)、红海束毛藻(Trichodesmium erythraeum)以及汉氏束毛藻(Trichodesmium hildebrandtii),其中铁氏束毛藻为优势种,胞内植生藻主要与根管藻(Rhizosolenia sp.)共生。冬季时束毛藻藻丝体平均丰度为0.194×104 filaments/L,束毛藻细胞平均丰度为0.172×106 cells/L,胞内植生藻细胞平均丰度为0.255×104 cells/L,与笔尖形根管藻(Rhizosolenia styliformis)共生的胞内植生藻居多;蓝藻主要分布在调查海域的北部。夏季时束毛藻藻丝体平均丰度为2.995×104 filaments/L,束毛藻细胞平均丰度为6.007×106 cells/L,胞内植生藻细胞平均丰度为2.198×104 cells/L,与笔尖根管藻共生的胞内植生藻占优势。夏季时固氮蓝藻丰度高于冬季,胞内植生藻宿主更为多样化。本研究中温度及冷窝对蓝藻的分布有重要影响,而盐度单独对蓝藻分布的影响不大,与温度结合时表现出一定的限制作用。     

Food and feeding habits of juvenile flounder Platichthys flesus (L.), abd turbot Scophthalmus maximus L. in the åland archipelago, northern Baltic Sea

The food choice of juvenile flounder (Platichthys flesus) and turbot (Scophthalmus maximus) was studied in the northern Baltic Sea during the years 1988, 1989, 1994 and 1995. The diet included organisms from 30 species/taxa in flounder (n = 306) and 10 species/taxa in turbot (n = 41). Flounder 45 mm mainly consumed meiofauna (dominating taxon: Harpacticoida, Copepoda) and larger fish (46–101 mm) consumed macrofauna (dominating taxa: Oligochaeta, Amphipoda and Chironomidae). In terms of biomass, macrofauna dominated for all sizes of flounders, and meiofauna was important only for the smallest fish. A strong seasonal variation could be detected in the diet. In spring, macrofauna dominated for all size classes of fish (only fish > 30 mm were caught in spring), while in summer and autumn meiofauna dominated the diets for fish 45 mm in size. Juvenile turbot (22–88 mm) consumed macrofauna and small fish. Turbot 30 mm consumed mainly amphipods, while > 30 mm turbot consumed mysid shrimps, amphipods and fish.The ontogenetic shift from meio- to macrofauna-sized prey in flounders occurs at a larger fish size in the northern Baltic Sea than reported in other areas, possibly depending on the increased relative importance of meiofauna in the northern Baltic. The seasonal variation in the diet could be due to seasonally changing abundances in the zoobenthos, or for the small fish (1-group, spring), to switching from meio- to macrofauna in order to optimize their energy gain. The 0-group flounders consumed meiofauna for a long period, possibly due to a learning-process or simply due to easy availability of meiofauna. Turbot has a much larger mouth gap than flounders, thus allowing them to consume macrofauna from the beginning of their benthic life.     

黄海中南部头足类的群落结构与生物多样性

为掌握黄海中南部头足类的群落结构及数量分布,作者根据2010~2011年间春、秋、冬3个季节的底拖网调查资料,对黄海中南部头足类的种类组成、生物量分布及生物多样性进行了研究。结果显示:3个季节共捕获头足类13种,隶属3目6科6属。各季节的优势种及其生物量比重分别为:春季——双喙耳乌贼(Sepiola birostrata)50.07%、秋季——针乌贼(Sepia esculenta)40.88%、冬季——枪乌贼(Loligo spp.)68.20%。各季节头足类平均资源密度分别为春季4.85 kg/km2、秋季2.52 kg/km2、冬季12.72 kg/km2,春秋两季间差异性不显著(P0.05),冬季与其他两季差异性显著(P0.05)。黄海中南部不同季节头足类的生物量分布变化较大,春季以西南及东北部密度最高,秋季以西南部密度最高,冬季以中部及东北部密度最高。头足类在各水深的垂直分布随季节变化。无论根据生物量还是丰度,种类丰富度指数、均匀度指数及Shannon-Wiener指数等多样性指数均以冬季最高,其次是春季,秋季最低。春季与冬季群落结构相似性较高,秋季与其他两个季节的群落结构相似性均较低。与1998~2000年同期相比,头足类种类数增加5种,相对资源密度增长了12%,枪乌贼类的生物量比重仍最高,耳乌贼类的比重提高,太平洋褶柔鱼的比重则大幅下降。     

Trophic relationships on a fucoid shore in south-western Iceland as revealed by stable isotope analyses, laboratory experiments, field observations and gut analyses

Rocky shores in the North Atlantic are known for their zonation patterns of both algae and animals, which can be expected to greatly affect food availability to consumers at different height levels on the shore. We tested the hypothesis that consumers would feed on the most abundant suitable food source in their surroundings. In total 36 species/taxa of common primary producers and consumers were sampled for stable isotope analyses from a sheltered fucoid shore at Hvassahraun in south-western Iceland. A selection of these species was also collected seasonally and from different height levels. Feeding experiments, field observations and gut analyses were also conducted. Our results were in good overall agreement with pre-existing knowledge of trophic relationships in the rocky intertidal. Consumers often appeared to be assimilating carbon and nitrogen from the most common diet in their immediate surroundings. The predator Nucella lapillus was thus feeding on different prey at different height levels in accordance with different densities of prey species. When tested in the laboratory, individuals taken from low on the shore would ignore the gastropod Littorina obtusata, uncommon at that height level, even when starved, while individuals from mid-shore readily ate the gastropod. This indicated that some kind of learned behaviour was involved. There were, however, important exceptions, most noteworthy the relatively small contribution to herbivores, both slow moving (the gastropod L. obtusata) and fast moving (the isopod Idotea granulosa and the amphipod Gammarus obtusatus) of the dominant alga at this site, Ascophyllum nodosum. The recent colonizer Fucus serratus seemed to be favoured. Selective feeding was indicated both by isotope signatures as well as by results of feeding experiments. Seasonal migrations of both slow and fast moving species could partly explain patterns observed.     

Dominant amphipods of Posidonia oceanica seagrass meadows display considerable trophic diversity

Gut content examination and trophic markers (fatty acids, stable isotopes of C and N) were combined to delineate the diet of the dominant species of amphipods from Mediterranean Posidonia oceanica seagrass meadows and to highlight trophic diversity among this community. Our results indicate that, although all dominant species heavily relied on macroalgal epiphytes, considerable interspecific dietary differences existed. Carbon stable isotope ratios notably showed that some of the amphipod species favored grazing on epiphytes from leaves or litter fragments (Apherusa chiereghinii, Aora spinicornis, Gammarus aequicauda), while others such as Dexamine spiniventris preferred epiphytes from rhizomes. The remaining amphipods (Caprella acanthifera, Ampithoe helleri and Gammarella fucicola) readily consumed both groups. In addition, SIAR modeling suggested that most species had a mixed diet, and relied on several food items. Fatty acid analysis and gut contents revealed that contributions of microepiphytic diatoms and of benthic and suspended particulate organic matter to the diet of amphipods were anecdotal. None of the examined species seemed to graze on their seagrass host [low 18:2(n‐6) and 18:3(n‐3) fatty acids contents], but Gammarus aequicauda partly relied on seagrass leaf detritus, as demonstrated by the lesser ¹³C‐depletion of their tissues. Overall, our findings suggest that amphipods, because of their importance in the transfer of organic matter from primary producers and detritus to higher rank consumers, are key items in P. oceanica‐associated food webs.     

岱衢洋拖网甲壳动物多样性的季节变化

根据2010年春季(5月)、夏季(8月)、秋季(11月)与2011年冬季(2月)对岱衢洋进行的共4个航次的底拖网渔业资源调查资料,对该海域的甲壳动物多样性进行了分析。结果表明,共捕获甲壳动物21种,其中虾类13种、蟹类7种、虾蛄类1种,隶属于2目14科18属;甲壳动物的生物量与尾数密度均以秋季为最高,春季则正好相反,且该两季的生物量与尾数密度间差异均显著(P<0.05);广温广盐种在种类数量、生物量与尾数密度方面均居主导地位;Margalef丰富度指数(D)、Shannon-Wiener多样性指数(H′)和Pielou均匀度指数(J′)的最小值均出现在冬季,表明该季甲壳动物群落的丰富度、多样性与均匀性都较低,另外,D值、H′值夏、秋两季高,冬、春两季低,与较外海域的情况正好相反,这主要是其对底层水温季节变化的一种响应。     

Grazing effects by Nereis diversicolor on development and growth of green algal mats

Nereis diversicolor is generally considered to be a predator and deposit feeder, but have also been found to graze on benthic algae in shallow coastal areas. In this study we investigated the grazing effects on the development and growth of green algae, Ulva spp. Algal growth was studied in an experiment including two levels of sediment thickness; 100 mm sediment including macrofauna and 5 mm sediment without macrofauna, and three treatments of varying algal biomass; sediment with propagules, sediment with low algal biomass (120 g dry weight (dwt) m^− 2) and sediment with high algal biomass (240 g dwt m^− 2). In the 100 mm sediment, with a natural population of macrofauna, N. diversicolor was the dominating (60% of total biomass) species. After three weeks of experimentation the result showed that N. diversicolor was able to prevent initial algal growth, affect growth capacity and also partly reduce full-grown algal mats. The weight of N. diversicolor was significantly higher for polychaetes in treatments with algae added compared to non-algal treatments. There were also indications that a rich nutrient supply per algae biomass counteracted the grazing capacity of N. diversicolor.     

刺参体壁脂肪酸组成的季节变化分析

对不同季节刺参(Apostichopus japonicus)体壁的脂肪酸组成进行了分析.结果表明刺参体壁的脂肪酸组成和相对质量分数具有明显的季节变化.在秋季和冬季,多不饱和脂肪酸(PUFA)的相对质量分数最高,其次是单不饱和脂肪酸(MUFA),饱和脂肪酸(SFA)的相对质量分数最低;春季MUFA的相对质量分数最高,其次是PUFA和SFA;夏季MUFA的相对质量分数最高,其次是SFA,PUFA的相对质量分数最低.在所有季节,相对质量分数最高的SFA和MUFA分别是16:0和16:1n-7,相对质量分数较高的PUFA是20:5n-3,20:4n-6和22:6n-3.n-3PUFA与n-6PUFA相对质量分数比值在1.87～2.42之间,冬季和春季显著高于夏季和秋季(P<0.05).