Composition, structural characteristics and temporal patterns of fish assemblages in non-tidal Mediterranean lagoons: A case study

The importance of transitional water ecosystems as nursery habitats and feeding grounds for fish species is well-known. Detailed studies of colonization patterns of fish guilds in response to biotic and abiotic drivers are however unevenly distributed among ecosystem types. We address here the temporal variability of fish assemblages in small non-tidal lagoons in the Mediterranean basin. The study was carried out at the Acquatina lagoon (Lecce, Italy) where four stations, situated in two habitat types along a confinement gradient, were sampled twice per month for one year with fyke nets. Forty-five taxa ranging across 20 families were collected, with the most abundant species, Atherina boyeri, accounting for more than 95% of total abundance. Pooling all species together (excluding sand smelt), the structural features of the assemblage, relative abundance of families, and abundance of individual species all showed significant temporal patterns. Mean abundance peaked in Summer and Autumn and fell in Winter, whereas taxonomic richness and diversity were highest in Summer and lowest in Spring. Within the fish assemblage, multivariate ordination showed temporal segregation of species belonging to the same family or genus and expected to be functionally similar, suggesting that they avoid competition for space and resources by timing inward migration and peak occurrence differently. Of the environmental driving forces, which also showed temporal patterns of variation, salinity was the main factor affecting the distribution of individuals and species. The catch of young individuals of several marine species confirmed the role of this small lagoon as a nursery and feeding area, and emphasized the need for further studies.     

Bait-attending fauna of the Kermadec Trench, SW Pacific Ocean: Evidence for an ecotone across the abyssal-hadal transition zone

The bait-attending fauna of the abyssal-hadal transition zone of the Kermadec Trench, SW Pacific Ocean (4329-7966 m), was investigated using a baited camera and a trap lander. The abyssal stations (4329-6007 m) revealed a typical scavenging fish community comprising macrourids and synaphobranchid eels, as well as natantian decapods. At the hadal depths of 7199 and 7561 m, the endemic liparid Notoliparis kermadecensis was observed aggregating at the bait reaching surprisingly high numbers of 5 and 13, respectively. A total of 3183 invertebrate samples were collected (mean deployment time=16 h) of which 97.8% were of the order Amphipoda (nine families, 16 species). Ten of the amphipod species represent new distributional records for the Kermadec Trench and the New Zealand Exclusive Economic Zone; this includes the shallowest known record of the endemic hadal amphipod Hirondellea dubia (6000, 6007 m). Using amphipods to statistically examine the compositional change across the abyssal-hadal boundary, an ecotone between depths <6007 and >6890 m was found, indicating that there is an ecologically distinct bait-attending fauna in this trench.     

秦皇岛七里海潟湖湿地非繁殖期鸟类多样性

2016年9月至2017年4月,采用样线法和可变大小样方法相结合,对七里海潟湖湿地非繁殖期鸟类进行了调查研究。调查共记录到鸟类13目27科60种,其中雀形目鸟类10科14种,占物种总数量的23. 33%;非雀形目鸟类17科46种,占物种总数量的76. 67%。湿地水鸟数量占全部鸟类总数量的95. 11%,水鸟类群主要为鸥类、雁鸭类、鸻鹬类和鹭类。鸟类居留类型主要为旅鸟和夏候鸟,分别占物种总数量的35. 00%和33. 33%。鸟类区系方面,以古北界鸟类和广布种鸟类为主,分别占物种总数量的63. 33%和26. 67%。经统计,鸟类多样性指数、均匀度指数和丰富度指数的平均值分别是1. 86、0. 39和2. 31。七里海潟湖湿地位于东亚—澳大利西亚迁徙路线上,是重要的鸟类迁徙停歇地和觅食地,鸟类尤其是水鸟资源丰富,应当受到关注和保护。     

Ecology of Nematodes in the Mediterranean Seagrass Posidonia oceanica (L.) Delile 1. General Part and Faunistics of the Nematode Community

Abstract. The nematode fauna of the phytal region of a stand of the Mediterranean seagrass Posidonia oceanica (L.) Delile was studied in a shallow subtidal location (5 m) at the island of Ischia (Gulf of Naples, Italy). During a one year's growth-cycle of the seagrass, abundance and faunal composition of the nematode community were investigated in a stratified sampling survey. Ninety seven species of nematodes were found. Nematode density and biomass ranged from 1.3 · 10⁵ indiv. · m^-2 (0.02g dwt · m^-2) in winter to 5.5 · 10⁵ indiv. · m^-2 (0.08 g dwt · m^-2) in early autumn. Density and biomass of nematodes were much lower and showed more marked seasonal fluctuations in the leaf strata than in the stem stratum of the seagrass. Diversity and seasonal homogeneity (expressed with Riedl 's index) were much lower in the two leaf strata (25–36 species, 29.6 ho%) than in the stem stratum (60–70 species, 42.5 ho%). The nematode community of the leaf stratum can be characterized as a Chromadora nudicapitata – Monhystrella sp. –Symplocostoma tenuicolle– community and is clearly set off from the stem stratum community (9.2% Riedl 's ho%), which is characterized as a Molgolaimus sp. 1 –Epsilonema sp. 1 –Chromadora nudicapitata– community. In the seasonal succession, the leaf stratum fauna shifts from a chromadorid-dominated community (from winter to summer) to a monhysterid-dominated community in early autumn. The stem stratum fauna shifts from a epsilonematid-dominated fauna in winter to a molgolaimid-dominated fauna in summer and early autumn. The distribution of nematode size classes showed a clear selection toward small animals (< 1 mm lenght), although marked seasonal fluctuations in size class distribution were observed. A modified approach for describing the trophic structure of the nematode fauna is presented. The observed abundance patterns and changes of community composition are discussed in relation to the development of habitat complexity and in relation to trophic conditions in the scagrass stand according to the seasonal growth rhythm of the plants and their aufwuchs-community.     

Diversity of faunal assemblages associated with ribbed mussel beds along the South American coast: relative roles of biogeography and bioengineering

Benthic organisms are among the most diverse and abundant in the marine realm, and some species are a key factor in studies related to bioengineering. However, their importance has not been well noted in biogeographic studies. Macrofaunal assemblages associated with subtidal beds of the ribbed mussel (Aulacomya atra) along South America were studied to assess the relationship between their diversity patterns and the proposed biogeographic provinces in the Southeastern Pacific and Southwestern Atlantic Oceans. Samples from ribbed mussel beds were obtained from 10 sites distributed from the Peruvian coast (17°S) to the Argentinean coast (41°S). The sampling included eight beds in the Pacific and two in the Atlantic and the collections were carried out using five 0.04 m² quadrants per site. Faunal assemblages were assessed through classification analyses using binary and log‐transformed abundance data. Variation in the size and density of mussels, and in the species richness, abundance and structure of their faunal assemblages were tested using a permutational multivariate analysis of variance. Faunal assemblages showed a north–south latitudinal gradient along both the Pacific and Atlantic coasts. Binary and abundance data showed a difference in the resulting clustering arrangement of Pacific sites between 40°S and 44°S, indicating a pattern of continuity in the species distribution associated with biological substrates. At a regional scale, the distribution of species along the South American coast matched the general provincial pattern shown by prior studies, which show two biogeographic units on the Pacific coast separated by an intermediate (probably transitional) zone and a single province on the Atlantic coast extending up to Northern Argentina. Biological substrates such as ribbed mussel beds play an important ecological role by making a similar habitat type available on a large scale for a variety of invertebrate species. Despite such habitat homogeneity, however, the associated fauna exhibit marked distribution breaks, suggesting strong constraints on dispersal. This therefore suggests that macrofaunal assemblages could possibly be used as biogeographic indicators.     

New records of cold‐water coral sites and fish fauna characterization of a potential network existing in the Mediterranean Sea

New cold‐water coral (CWC) sites were recorded along the Apulian margin (Central Mediterranean). The species composition and depth distribution of CWCs were updated. A distribution of the CWC sites coincident with the course of the dense‐water masses that flow between the Southern Adriatic and Northern Ionian was confirmed. The faunal assemblages of five of these CWC sites were investigated and compared using experimental longlines during the spring–summer and autumn–winter seasons, between 2010 and 2014. Differences in ecological variables amongst the sites in each season were evaluated by means of a set of univariate and multivariate methods (analysis of variance, permutational multivariate analysis of variance, non‐metric multidimensional scaling). Although some differences were detected in relation to the different depths examined during spring–summer, the CWC sites showed similar features in terms of species richness and diversity as well as in the abundance of the same fish species (Galeus melastomus, Conger conger, Helicolenus dactylopterus, Merluccius merluccius, Phycis blennoides and Pagellus bogaraveo) most probably because of the distribution of adult specimens in structurally complex and heterogeneous habitats, which act as a potential ‘refuge network’ with respect to commercial fishing. The presence of maturing and mature individuals as well as post‐reproductive females indicates that these CWC sites also act as spawning areas, representing a potential ‘renewal network’ for the fish populations. The term ‘network’ used here refers to several similar subsystems (CWC sites) that play the same ecological role in a wider system (Apulian margin). These CWC communities need coherent conservation measures and management strategies according to the Ecosystem Approach to Fisheries.     

Riverine dominance of a nearshore marine demersal food web: evidence from stable isotope and C/N ratio analysis

The Thukela Bank, KwaZulu-Natal, supports a diverse ecosystem and South Africa’s only prawn fishery. Oceanographic studies suggest riverine input is not important for the biology of this system, whereas biological studies suggest the contrary, with prawn catches increasing with increased fluvial run-off. The aim of this study was to determine (i) the importance of riverine and marine organic matter for the Thukela Bank food web; and (ii) whether there are seasonal changes in the Thukela River stable isotope values, and, if so, whether these are reflected in the isotope values of demersal organisms. Estuarine organic matter, sediments and demersal organisms were collected from several sites across the bank in the wet and dry seasons of 2008, 2009 and 2010. Marine particulate organic matter was also collected in 2010 and analysed for δ13C and δ15N, as well as C/N ratios. There were strong seasonal changes in isotopic values of organic matter and fauna, especially faunal δ13C. There was an apparent time-lag in organisms assimilating riverine organic matter isotopic values, with the isotopic signature of demersal organisms reflecting that of riverine organic matter from the previous season, which is likely the result of tissue turnover time. In 2010, Thukela Bank sediment organic matter was of riverine origin and this maintained the demersal food web. We conclude that Thukela River organic matter is an important input to the food web of the Thukela Bank, indicating that any future damming of the catchment area could have serious consequences for this ecosystem.     

Use of submerged aquatic vegetation as habitat by young-of-the-year epibenthic fishes in shallow Maine nearshore waters

Epibenthic fishes were collected with daytime beam trawl tows (n = 1713) in three shallow (<10 m) habitats of submerged aquatic vegetation (SAV), Zostera marina (eelgrass), Laminaria longicruris (kelp), Phyllophora sp. (algae), and unvegetated sandy/mud areas. We divided the Maine coast into three broad zones based upon geological features and sampled over five consecutive years; during April–November 2000 in the mid coast, in 2001 and 2002 along the south coast and in 2003 and 2004 along the eastern Maine coast. We quantified habitat use by eight economically important fish species (Gadus morhua, Microgadus tomcod, Pollachius virens, Urophycis chuss, Urophycis tenuis, Osmerus mordax, Tautogolabrus adspersus, and Pseudopleuronectes americanus) and 10 other common epibenthic species (n = 18 571). We identified the physical and biological variables most important in discriminating between habitats with and without individual fish species. Logistic regression models based on nearshore habitat characteristics were developed to predict the distribution of these species along the three zones representing broad geological regions of the Maine coast. Logistic regression models correctly classified individual fish species 58.7–97.1% of the time based on the temporal and physical habitat variables (month, temperature, salinity, and depth) and the presence–absence of submerged aquatic vegetation (Zostera, Laminaria, or Phyllophora). Overall fish presence and economically important fish presence were correctly classified 61.1–79.8% and 66.0–73.6% of the time, respectively. The Maine shallow water fish community was composed primarily of young-of-the-year and juvenile fishes with all habitats functioning as facultative nursery areas. Presence of most fish species was positively associated with Zostera, Laminaria, and to a lesser extent, Phyllophora. This study provides direct evidence of shallow waters of the Gulf of Maine as critical facultative nursery habitat for juvenile G. morhua, M. tomcod, P. virens, U. tenuis, U. chuss, T. adspersus, O. mordax and P. americanus, and many ecologically important species.     

Benthic community and biological trait composition in respect to artificial coastal defence structures: A study case in the northern Adriatic Sea

Biological Traits Analysis (BTA) is a method for addressing ecological functioning based on traits exhibited by members of biological assemblages. This study explores and compares species and biological trait patterns on either side (landward and seaward) of coastal breakwater structures in northwestern Adriatic Sea (Italy), with the aim of giving insights and knowledge for management of sandy beach systems affected by coastal development. Eight ecological traits of 96 benthic species were considered. Taxon composition evidenced differences in benthic assemblages across time and exposure: landward and seaward communities shared less than 50% of the total number of species. BTA suggested a no-management effect in the functioning of benthic assemblages. Dominant traits modalities were deposit-feeding, short life, small body size, short life span, iteroparity, gonocorism, with plankto-planktotrophic larvae. The results of BTA highlighted similarities and stability in trait composition contrary to species composition, suggesting a possible persistence in benthic functioning despite the occurrence of species replacements. To best of my knowledge, this study is one of the first attempts to investigate the effects of a management measure (submerged shore-parallel barriers with groynes) in a shallow marine system by means of BTA.