The Amphipod Community as a Bioindicator in Algeciras Bay (Southern Iberian Peninsula) Based on a Spatio-Temporal Distribution

Abstract. The amphipod population associated with Bugula neritina (L.), a verycommon bryozoan species in Algeciras Bay (Strait of Gibraltar), was studied on a spatio-temporal scale, in order to define its role as a bioindicator. Samples were collected in December, March, June and September along a transect running from the external to the internal sampling stations.
Fifty-three species belonging to 22 families were identified; the most abundant species were Jassa marmorata H olmes , Ischyrocerus inexpectatus (R uffo ) and Phtisica marina S labber .
The spatial evolution of the amphipod community reflected the physico-chemical conditions of Algeciras Bay, yielding a clear gradient from the outer to the inner stations. The stations located at the mouth of the bay, characterised by high hydrodynamism and low sedimentation, had a higher diversity and species richness than the inner stations with low water movement and higher sedimentation. Eight species preferred for the outer stations, while another nine species were typical of the inner harbours.
The most notable aspect of the seasonal evolution was the increased dominance of the tube-builder and deposit-suspension feeder Jassa marmorota .
Structural and ordination analyses corroborate the outer-inner gradient in the bay and illustrate the importance of hydrodynamic forces and sedimentation in the amphipod community.     

Vertical distribution and seasonality of peracarid crustaceans associated with intertidal macroalgae

Spatial patterns and seasonal fluctuations of intertidal peracarids from Tarifa Island, Strait of Gibraltar, were studied over a two-year period (December 2005–December 2007). A total of 25,749 individuals were collected, comprising 46 species. Amphipods were best represented in the total number of species (32) and individuals (89% of numerical abundance) followed by isopods (12 species and 11% abundance) and tanaids (2 species and 1%). The highest number of species was registered in intermediate levels (1–1.5 m) dominated by Corallina elongata, although the highest abundances of peracarids were associated to seaweeds of lower levels (0–1 m) such as Gelidium corneum, Osmundea pinnatifida, Valonia utricularis and a turf of Caulacanthus ustulatus. The most abundant peracarids, Hyale stebbingi, H. schmidti, H. perieri, Stenothoe monoculoides, Caprella penantis, C. grandimana, Dynamene edwardsii and Ischyromene lacazei, were present throughout the whole year during 2006 and 2007. The highest peracarid densities were measured in April–August coinciding with the highest development of seaweeds, just before the maximum values of water temperature measured at the end of summer. Multivariate analyses confirmed a clear zonation of algae and associated peracarids in a vertical gradient, which was maintained stable during the two-year study. Several physical and biological factors may regulate such patterns of peracarid abundance and future experimental studies are necessary to explore the importance of factors such as competition, predation or weather conditions.     

Spatial distribution of crustaceans associated with shallow soft‐bottom habitats in a coral reef lagoon

The ecology and diversity of the shallow soft‐bottom areas adjacent to coral reefs are still poorly known. To date, the few studies conducted in these habitats dealing with macroinvertebrate fauna have focused on their abundance spatial patterns at high taxonomic levels. Thus, some aspects important to evaluate the importance and vulnerability of these habitats, such as species diversity or the degree of habitat specialization, have often been overlooked. In this study we compared the crustacean assemblages present in four different habitats at Magoodhoo Island coral reef lagoon (Maldives): coral rubble, sandy areas and two different seagrass species (Thalassia hemprichii and Cymodocea sp.). Forty‐two different crustacean species belonging to 30 families and four orders were found. ‘Site’ was a significant factor in all of the statistical analyses, indicating that tropical soft‐bottom habitats can be highly heterogeneous, even at a spatial scale between tens and hundreds of meters. Although traditionally it has been considered that seagrass beds host greater species diversity and abundance of organisms than adjacent unvegetated habitats, no differences in the univariate measures of fauna (abundance of organisms, number of species and Shannon diversity) were observed among habitats. However, sandy areas, coral rubble and seagrass beds exhibited different species composition of crustacean communities. The percentage of taxa considered as potential habitat specialists was 27% and the number of species exclusively occurring in one habitat was especially high in seagrass beds. Thus, degradation of this vegetated habitat would result in a great loss of biodiversity in tropical shallow soft‐bottom habitats.     

Morphology and structure of the Camarinal Sill from high-resolution bathymetry: evidence of fault zones in the Gibraltar Strait

The Gibraltar Strait is the very narrow neck which connects the Atlantic Ocean and the Mediterranean Sea. The causes and mode of its opening at the end of the Messinian Salinity Crisis are still a matter of debate, and models based on eustatic rise and/or topographic lowering due to either erosion or faulting are generally evoked. We investigated the presence of faults based on a morphological and structural analysis of the Camarinal Sill, the shallowest passage in the Gibraltar Strait (<100 m water depth in places). This sill connects the Spanish and Moroccan shelves, and probably represents a structural high inherited from the Miocene compressive tectonics which took place in the external zones of the Betic-Rif orogenic arc. Our high-resolution bathymetric data enabled us to identify and interpret the origin of major morphological features in the area, including canyons, channels and a landslide, which we name the Tarifa landslide. Topographic arguments suggest that the Camarinal Sill is crossed by two main E-W- to ENE-WSW-directed fault zones which bound areas with different distribution, orientation and slopes of both scarps and crests. We name these the Hercules and Tarik fault zones, north and south of the sill respectively. The Hercules fault zone probably incorporates a normal movement component, whereas kinematic indicators are poor along the Tarik fault zone. The age of faulting is poorly constrained in both cases. Together with existing evidence of faults onland, the presence of these fault zones implies that they could be responsible for, or have contributed to, the opening of the Gibraltar Strait.     

Metal fluxes through the Strait of Gibraltar: the influence of the Tinto and Odiel rivers (SW Spain)

A large set of new data concerning dissolved metal concentrations has been acquired in the Gulf of Cadiz and in the Strait of Gibraltar from 1996 to 1999. These data, associated with models (hydrodynamic, tracer advection–dispersion and mixing), have been used to assess the influence of rivers draining the South Iberian Pyrite Belt on the Gulf of Cadiz and on the Atlantic inflow in the Strait of Gibraltar.Metal concentrations in surface waters from the Gulf of Cadiz are maximal near the mouth of the Tinto/Odiel rivers with values exceeding 50 nmol/kg (Mn), 5 nmol/kg (Ni), 30 nmol/kg (Cu), 100 nmol/kg (Zn), 0.9 nmol/kg (Cd) and 45 nmol/kg (As). From the Tinto/Odiel river, a plume of contamination follows the coast in the direction of the Strait of Gibraltar. The computation of a tracer advection–dispersion model confirms that the coastal currents carry the metals discharged from the Tinto and Odiel to the Strait of Gibraltar.From temperature–salinity and metal–salinity plots, four water masses can be recognised in the Gulf of Cadiz and in the Strait of Gibraltar: North Atlantic Surface Water (NASW), North Atlantic Central Water (NACW) and metal-enriched Spanish Shelf Waters from the Gulf of Cadiz (SSW). The Mediterranean Outflow Water (MOW) is also clearly seen at depths greater than 300 m.The chemical characteristics of these various water masses have been used in a mixing model to evaluate their relative contribution to the Atlantic inflow through the Strait of Gibraltar. These contributions are seasonally variable. In June 1997, the contribution was: 80±20%, 5±5% and 15±10% for NASW, NACW and SSW, respectively. In September, the SSW contribution was apparently negligible.Finally, these relative contributions allow the evaluation of the metal fluxes in the Strait of Gibraltar. The presence of SSW in the Strait increases the metal flux to the Mediterranean Sea by a factor of 2.3 (Cu), 2.4 (Cd), 3 (Zn) and 7 (Mn). It does not modify significantly As and Ni fluxes.     

A fine resolution model of the eastern North Atlantic between the Azores,the Canary Islands and the Gibraltar Strait

The region of the North Atlantic between the Azores, the Canary Islands and the Gibraltar Strait is the subject of the multidisciplinary CANIGO project. A fine resolution primitive equation level model, called the CANIGO regional model, has been constructed to help with the integration of the observations. The model has open boundaries on three sides and at the Strait of Gibraltar.The output from the regional model gives a good representation of the Azores Current, the variability around Madeira, the Canary Current and the associated upwelling, the Cape Ghir and other cool filaments, and the spreading of Mediterranean Water. After passing south of the Azores, the Azores Current splits into two branches. The northern branch meanders towards the Gulf of Cadiz and the Gibraltar Strait, and the southern branch passes south of Madeira and through the Canary Archipelago.     

南麂列岛环境质量调查与潮间带生态研究

１９９２年５月～１９９３年３月对南麂列岛潮间带１７条断面和本岛陆域环境进行了全面的生态调查和环境质量评价。共获大型底栖动物２７８种，大型藻类１２１种，微小型藻类１５５种。研究结果表明，本区种类组成以软体动物最为丰富，生物数量以甲壳动物占绝对优势。区系特点与福建、广东沿岸较为相似。生物量以春季为高，栖息密度在秋季有一明显高峰。生物量的大小顺序为开敞岩礁大于隐蔽岩礁大于巨砾大于泥滩大于沙滩。种类组成、数量分布和群落结构与底质类型、波浪作用关系密切。文中还对生物的地域断裂分布现象作了探讨，对环境质量保护问题提出了建议。     

西沙群岛海产蓝藻类的研究Ⅰ

我国西沙群岛海产蓝藻类的种类极为丰富。但迄今为止除黎尚豪报导过西沙群岛永兴岛的陆生习性的27种蓝藻外,尚未见过任何报告。本文为西沙群岛海产蓝藻类研究的第一部分。根据的材料是中国科学院海洋研究所1975年和1976年在西沙群岛采集的,计127号。本文仅报道11种,隶于颤藻科(Oscillatoriaceae)的6属,其中4种在我国为海产蓝藻的新记录。     

Seasonal variability of water transport through the Straits of Gibraltar, Sicily and Corsica, derived from a high-resolution model of the Mediterranean circulation

The variability of the water transport through three major straits of the Mediterranean Sea (Gibraltar, Sicily and Corsica) was investigated using a high-resolution model. This model of the Mediterranean circulation was developed in the context of the Mercator project.The region of interest is the western Mediterranean between the Strait of Gibraltar and the Strait of Sicily. The major water masses and the winter convection in the Gulf of Lions were simulated. The model reproduced the meso-scale and large-scale patterns of the circulation in very good agreement with recent observations. The western and the eastern gyres of the Alboran Sea were observed but high interannual variability was noticed. The Algerian Current splits into several branches at the longitude of the Strait of Sicily level, forming the Tyrrhenian branch, and, the Atlantic Ionian Stream and the Atlantic Tunisian Current in the eastern Mediterranean. The North Current retroflexed north of the Balearic Islands and a dome structure was observed in the Gulf of Lions. The cyclonic barotropic Algerian gyre, which was recently observed during the MATER and ELISA experiment, was evidenced in the simulation.From time-series of 10-day mean transport, the three straits presented a high variability at short time-scales. The transport was generally maximum, in April for the Strait of Gibraltar, in November for the Strait of Sicily, and in January for the Strait of Corsica. The amplitudes of the transport through the Straits of Gibraltar (0.11 Sv) and Sicily (0.30 Sv) presented a weaker seasonal variability than that of the Strait of Corsica (0.70 Sv).The study of the relation between transport and wind forcing showed that the transport through the Strait of Gibraltar is dependent on local zonal wind over short time-scales (70%), which was not the case for the other straits (less than 30%). The maximum (minimum) of the transport occurred for an eastward (westward) wind stress in the strait. An interannual event was noticed in November–December 2001, which corresponded to a very low transport (0.3 Sv), which was characterised by a cyclonic circulation in the western Alboran Sea. That circulation was also reproduced by the model for other periods than winter during the interannual simulation.The transport through the Strait of Sicily is not influenced by local wind.The wind stress curl of the northwestern Mediterranean influenced the transport through the Strait of Corsica.     

Biological features of Pupu Springs

The flora and fauna of Pupu Springs (40°51'S, 172° 46'E) and five other New Zealand cold springs are described. In Pupu Springs there are 16 species of algae, 10 species of bryophytes (including three species of liverworts), and 5 species of angiosperms. The fauna includes a phreatic form (an eyeless planarian, Dugesia sp.), a possible glacial relict (the caddis fly Rakiura vernale), and cold stenotherms (e.g., the caddis fly Psilochorema tautoru). The most abundant animals in the New Zealand springs are Mollusea, Crustacea, and’ larvae of Plecoptera, Diptera, and Trichoptera.

Pupu Springs consist of five biotopes and associated biocoenoses.     

Flow variability in the Strait of Gibraltar: The Mediterranean adjustment to tidal forcing

The vertical structure of the flow variability through the Strait of Gibraltar is studied based on the Gibraltar Experiment and the Word Ocean Circulation Experiment data sets. An analysis of the leading modes of velocity and density variability at the Strait of Gibraltar showed an adjustment of the water masses exchanged through the Strait. Mediterranean mass variations resulting from the water exchanged by barotropic tidal oscillations generate changes of the baroclinic component of the flow that damp these mass variations. This adjustment explains the previously observed fortnightly variation of the shear. Moreover, the adjustment is found to operate for the subinertial time scale flow variability forced by the atmospheric pressure. An analytical model aimed at reproducing variations of the velocity with time and in the vertical is derived. The model includes a depth-varying parameterisation of friction and takes into account density gradient fluctuations across the Strait. The model reproduces the main features of the flow, in particular the shear and the interface depth variations with the tide phase.     

A PRELIMINARY STUDY ON FAUNA OF PLANKTONIC COPEPODS IN THE CHINA SEAS

A total of 345 species of planktonic copepods have hitherto been found from the China Seas. Among them, tropical and warm-water species are dominant. The similar pattern of geographical distribution of these species is ascribed to the common influence of the coastal currents, the Kuroshio, and the South China Sea warm current. The number of species of planktonic copepods along the coastal waters of China decreases with increasing latitude, and increases with increasing longitude. The composition of the copepod fauna in the China Seas shows that the Bohai Sea and the northern Huanghai Sea belong to the north temperate zone fauna, that the South China Sea, offshore areas of the East China Sea and the southeastern part of the Taiwan Strait belong to the tropical fauna, and the western part of the Taiwan Strait and the northwestern part of the East China Sea belong to the mixed distribution area of tropical and subtropical fauna.     

Spawning hoki (Macruronus novaezelandiae Hector) concentrations in Cook Strait and off the east coast of the South Island,New Zealand,August‐September 1987

Abstract

In September 1986, dense concentrations of freshly spawned hoki (Macruronus novaezelandiae) eggs were located in eastern Cook Strait. A follow‐up exploratory trawl survey of Cook Strait and the east coast of the South Island, in August and September 1987, located concentrations of spawning hoki in canyon features in Cook Strait, off the Kaikoura coast, and off Banks Peninsula. The largest concentration, 14 km long, 4 km wide, and up to 150 m thick occurred in Cook Strait Canyon, with catch rates of hoki up to 48 t h^?1. Gonad conditions of male and female hoki showed they were actively spawning. Catch rates in Cook Strait Canyon were comparable to the main fishery on the west coast of the South Island but were much lower off Kaikoura and Banks Peninsula. Hoki associated with spawning concentrations were not feeding. Bycatch species were mostly ling (Genypterus blacodes) and spiny dogfish (Squalus acanthias), and both were preying on hoki. Spiny dogfish were also feeding on spawned fish eggs. The possible stock structure of hoki is discussed.     

浙江檀头山岛周围海域夏、秋季大型底栖动物群落结构特征

为揭示现阶段浙江檀头山岛周围海域大型底栖动物群落现状,于2013年7月、2013年11月对该海域进行了2航次的大型底栖动物生态调查,20个采样站位共获得大型底栖动物55种,其中甲壳动物最多,有18种(占32.73%),其次是底栖鱼类(17种,占30.91%)、软体动物(16种,占29.09%),腔肠动物3种(5.45%),环节动物最少,只有1种(1.82%)。2航次共鉴定大型底栖动物优势种14种,其中葛氏长臂虾Palaemon gravieri、细巧仿对虾Parapenaeopsis tenella为2航次共有优势种,其余均为单一航次优势种,夏、秋季间种类更替率较高,为51.85%。平均生物量、丰度,夏季航次均分别高于秋季航次,方差分析表明生物量、丰度两航次间均存在显著差异(P0.05),远近岸间均不存在显著差异(P0.05)。对檀头山岛周围海域夏季和秋季大型底栖动物群落结构进行聚类分析和n MDS排序分析,结果表明,夏季、秋季20个站位均可划分成2个主要聚类组,对各聚类组内平均相似度贡献较大的物种主要是广温、广盐性的甲壳类动物,如东方口虾蛄Oratosquilla oratoria、中国毛虾Acetes chinensis、细螯虾Leptochela gracilis、葛氏长臂虾Palaemon gravieri、中华管鞭虾Solenocera crassicornis、三疣梭子蟹Portunus trituberculatus等。ABC曲线和多样性指数分析表明,檀头山岛周围海域大型底栖动物群落在秋季受到重度扰动,夏季未受到扰动。粒径分析结果显示檀头山岛周围海域沉积物主要是由较细颗粒的黏土和粉砂组成。CCA分析结果表明温度、盐度、水深、溶解氧是对大型底栖动物影响程度较大的环境因子。     

Community structure and functional traits of mollusks associated with coastal reef macroalgae in Northeastern Brazil

This study investigated the community structure and functional traits of the mollusk fauna associated with macroalgae with different thallus morphologies in a reef environment in Northeastern Brazil. A total of 15 individuals of each species of macroalgae adhered to natural substrate and 15 individuals of Padina gymnospora detached from the substrate were collected. The structural complexity of algal habitats was measured and the associated malacofauna screened and identified. All three macroalgae differed significantly in the complexity of their habitat, with Sargassum polyceratium being the most complex. A total of 823 specimens of mollusks belonging to 22 species and 11 families were recorded, of which Columbellidae was the most represented with six species. The functional trait “size” revealed that micromollusks smaller than 10 millimeters were predominant in the community; however, individuals of larger sizes (up to 24.54 millimeters) belonging to young stages of other species were also present. Eight functional trophic groups were identified, of which “carnivorous” stood out with seven species. Six functional groups of microhabitats were identified, with intra‐specific variation in habitats, while habitat expansion was documented for species not yet recorded in association with macroalgae. The structure of the molluskan community differed among the three algae species with the greatest richness, abundance, and diversity of mollusks and functional traits occurring with S. polyceratium. Community structure differed between algae adhered to natural substrate and detached algae, with the latter having lower mollusk richness and diversity, but with greater abundance of some species that remained on algal fronds after release from the reef environment. This study reinforces the importance of algal habitat for marine invertebrate fauna, especially for micromollusks that spend their entire life cycle, or part of it, in association with macroalgae.     

Effects of temporal variation of the seaweed Caulerpa prolifera cover on the associated crustacean community

The aim of this study was to establish the effect of temporal variation of the alga Caulerpa prolifera cover on the composition and stability of the associated crustacean community. Forty‐five crustacean species were found, amphipods and tanaidaceans being the most abundant groups. The stations were grouped mainly based on the gradient of algal cover, independently of location or sampling period (MDS analyses). Considering separately epifaunal and infaunal species, the epifauna occurred mainly at high cover (HC) and medium–low cover (MLC) stations, while the infauna occurred at MLC and unvegetated (UV) stations. Infaunal species were predominant in all stations and sampling periods, and the abundance and numbers of epifaunal species showed a clear dependence of algal cover. To quantify the loss of biodiversity due to the plant cover variations, we applied the average and variation in taxonomic distinctness (Δ⁺ and Λ⁺, respectively). The HC stations, especially those with fewer algal cover variations along the study period, showed few fluctuations of Δ⁺,and Λ⁺ was usually located near mean; however, UV stations tended to fall in the area where the statistical power of the test is reduced and showed more oscillations of Λ⁺. The ability of these indices to test the fauna composition in function of the alga presence is discussed.     

Mesoscale coupling between planktonic cnidarian distribution and water masses during a temporal transition between active upwelling and abatement in the northern Benguela system

The composition and spatio-temporal distribution of planktonic cnidarians in the northern Benguela system are described from plankton samples collected on four cruises between December 1981 and March 1982. The sampling period was characterized by initially active coastal upwelling, followed by abatement of upwelling. In all, 20 species of medusae and 24 species of siphonophores were identified. The most abundant medusae were Chrysaora hysoscella, Aequorea aequorea and Liriope tetraphylla, and the most abundant siphonophores were Muggiaea atlantica, Abylopsis tetragona and Bassia bassensis. Three assemblages of planktonic cnidarians were differentiated. The first was associated with coastal upwelling and consisted of the medusae Proboscidactyla menoni, Aglauropsis edwardsii and juvenile C. hysoscella, along with the siphonophore M. atlantica. The second assemblage was associated with oceanic water and the component species were indicative of the offshore influence of the Benguela system; L. tetraphylla and most of the siphonophores belonged to this assemblage. The third assemblage consisted of species typical of shelf fauna, namely A. aequorea, Mitrocomella grandis and adult C. hysoscella, all also typical of the northernmost waters of the Benguela system. Overall, there was coupling between mesoscale hydrographic features and the pattern of distribution of cnidarian populations, with a distinct cross-shelf gradient that was more pronounced during active upwelling.     

Living (Stained) Benthic Foraminifera and their Response to the Seasonal Hydrographic Cycle, Periodic Hypoxia and to Primary Production in Havstens Fjord on the Swedish West Coast

Havstens Fjord on the Swedish west coast is a silled fjord that is characterized by strong stratification and stagnant bottom-water with periodically occurring hypoxic (0–2 ml l⁻¹) or anoxic (≤0 ml l⁻¹) conditions. Renewal of Havstens Fjord's deep-water occurs every year, mostly during winter or spring. The aim of this study was to discover how living benthic Foraminifera respond to hydrographic variations, periodic oxygen deficiency and variations in primary production. A long series of monthly hydrographic measurements combined with sediment sampling were performed from August 1993 to December 1994. Sampling was carried out at four different sites along a depth transect (12, 20, 30 and 40 m). Monthly values of chlorophyll a from the water surface down to 15 m were obtained. With increasing water depth, the foraminiferal fauna changed from a low diverse brackish fauna, through a diverse and abundant fauna, to a low diversity and sparse fauna characterized by species tolerant of oxygen depletion. At the deepest site (40 m) Elphidium magellanicum and Stainforthia fusiformis survived five months of anoxic or near anoxic conditions. At 30 m the periodic hypoxic conditions were severe enough to prevent a rich benthic macrofauna establishing, but there was enough oxygen for an abundant and diverse foraminiferal fauna to thrive. Under oxic conditions, freshly sedimented phytoplankton seem to be an important food source for the Foraminifera.     

Macrofauna associated to Mycale microsigmatosa (Porifera, Demospongiae) in Rio de Janeiro State, SE Brazil

The macrofauna (endo- and epi-biotic) associated to the sponge Mycale (Carmia) microsigmatosa Arndt, 1927 was studied at three sites in Rio de Janeiro State, Brazil (Arraial do Cabo, Niterói, and Rio de Janeiro). A total of 2235 individuals (over 1 mm long) of 75 invertebrate species were found associated to 19 specimens of the sponge. The most abundant and diverse taxa were the crustaceans (83%, 31 spp.), polychetes (10%, 18 spp.), and molluscs (3.7%, 15 spp.). Cnidarians, platyhelminthes, ascidians, echinoderms, pycnogonids, bryozoans, and sponges were also represented. Amphipod crustaceans were the dominant group, comprising 61% of all individuals collected. Species richness and abundance of associated fauna were highly correlated with sponge volume, but diversity and evenness were not. The site of collection influenced the species composition of the fauna associated to M. microsigmatosa but did not change significantly its diversity, abundance, richness, and dominance patterns of higher taxa. Pregnant females and juvenile stages of 29% of the species associated, including crustaceans, molluscs, echinoderms, and pycnogonids were frequently found inside M. microsigmatosa. Although many of these organisms do occur and reproduce in other habitats outside the sponge as well, M. microsigmatosa is also important for their reproduction and survivorship, thus contributing for the maintenance of biodiversity in Southwestern Atlantic sublittoral rocky shores.     

大管岛礁区潮下带大型底栖海藻群落的初步研究

1990年5月和11月对大管岛礁区潮下带大型底栖海藻进行了两次定量调查。共采到23种大型海藻，其群落构成以红藻类占优。海藻种类的区系温度性质属明显的温水性区系。5月份平均生物量为240．939／m2，11月份平均生物量为164．399／m2。两季度月都以岛西侧的D7断面平均生物量最高，分别为820．159／m2和472．509／m2。就垂直分布而言，1—2米水层内海藻分布密度最高，达527．549／m2。优势种为海蒿子和石花菜。