Tethya (Porifera,Demosponglae) Species Coexisting in a Maldivian Coral Reef Lagoon: Taxonomical,Genetic and Ecological Data

Abstract. Tethya microstella, T. orphei, T. robusta, and T. seychellensis live in sympatry in a Maldivian coral reef lagoon (Gangehi Island, Ari Atoll). A morphological, morphometric, and electrophoretical study of these species show that their Maldivian populations are well separated morphologically and genetically. The genetic distances and the other data are more consistent with an immigration than with a local speciation hypothesis. Their coexistence may be explained by a differentiation in ecological requirements. The four species inhabit the shallow water biotope of the lagoon among the rubble of dead corals. Our data show that T. orphei and T. seychellensis occupy the upper rubble layer, T. microstella and T. robusta the lower one. This distinction agrees with the different morpho-functional features of the two pairs of species.     

Adaptive Ecology, Growth Strategies and the Global Bloom Expansion of Dinoflagellates

Dinoflagellates exhibit unique differences from diatoms in their adaptive ecologies that may be favoring their increasingly successful exploitation of coastal waters and global bloom expansion. Dinoflagellates behave as annual species, bloom soloists, are ecophysiologically diverse and habitat specialists, whereas diatoms behave as perennial species, guild members and are habitat cosmopolites. Diatoms have a relatively uniform bloom strategy based on species-rich pools and exhibit limited habitat specialization. Dinoflagellates have multiple life-form strategies consistent with their diverse habitat specializations, but rely on impoverished bloom species pools. Niche structure and dinoflagellate competition for niche space are considered. The “open niche period” formulated originally for Narragansett Bay is extrapolated as a general bloom paradigm. It is suggested that successful niche occupancy leading to blooms involves adaptive strategies at three heirarchic taxonomic elements: phylogenetic, generic and species-specific, and in that sequence. Transoceanic expatriation of emigrant species leading to indigenous status and blooms requires completion of a three-stage colonization process. Anthropogenic seedings are not, in themselves, bloom stimulation events; they are only the first phase of a multiple-step process. The organismal and niche features required for a hidden flora member to become a bloom species are considered, and the interplay between niche structure, habitat carrying capacity, colonization requirements and stochasticity as factors in the changing global bloom behavior of dinoflagellates discussed. The question is posed whether traditional perspectives of phytoplankton behavior apply completely to dinoflagellates. This revised version was published online in August 2006 with corrections to the Cover Date.     

Feeding behavior in Caribbean surgeonfishes varies across fish size,algal abundance,and habitat characteristics

Feeding behavior of coral reef fishes often determines their species‐specific ecological roles. We studied the two most common Caribbean surgeonfishes (Acanthurus coeruleus and Acanthurus tractus) to examine their species‐specific grazing rates and feeding preferences and how these differed with environmental context. We quantified the feeding activity of both surgeonfishes at four spur and groove reefs in the Florida Keys, USA, that varied in fish abundance, rugosity, algal community composition, and sediment loading. Overall, A. tractus fed twice as fast as A. coeruleus. Both species selected for turf algae but avoided feeding on turf algae that had become laden with sediment. Selectivity for upright macroalgae was more complex with A. tractus targeting Dictyota spp., while A. coeruleus avoided Dictyota spp. relative to the alga's abundance. Both species selected for epiphytes growing on other organisms such as macroalgae and sponges. However, several of these feeding patterns changed with ontogeny. For example, larger individuals of both species fed more frequently on long, sediment‐laden algal turf and less frequently on Dictyota spp. compared to smaller sized individuals. In addition, A. tractus also increased its preference for upright calcareous algae as they attained larger sizes. Overall, the disparity in feeding preferences of surgeonfishes likely indicates subtle differences in species‐specific ecological roles. Both A. coeruleus and A. tractus likely prevent development of turf algae and thus maintain algal communities in the early stages of succession. Additionally, A. tractus may also help reduce macroalgal abundance by targeting common macroalgal species.     

浙南岛屿岩相潮间带大型底栖动物优势种生态位研究

本研究利用1990年、2006年、2010年和2016年11月在南麂列岛、北龙-北麂列岛和洞头列岛的调查结果和历史资料,分析了浙南岛屿岩相潮间带大型底栖动物优势种的时空变化及生态位.结果显示:4次调查数据中主要优势种有15种,前4位优势种分别为日本笠藤壶、条纹隔贻贝、疣荔枝螺和小结节滨螺;30 a来日本笠藤壶有逐渐被条...     

A preliminary study of habitat and resource partitioning among co-occurring tropical dolphins around Mayotte, southwest Indian Ocean

Mayotte in the southwest Indian Ocean is characterized by high dolphin diversity. They may coexist within a fairly small area around the island because they exploit neither the same preferential habitats nor the same resources. This preliminary study aimed to investigate ecological niche segregation among these delphinid communities: the Indo-Pacific bottlenose dolphin, Tursiops aduncus, the pantropical spotted dolphin, Stenella attenuata, the spinner dolphin, Stenella longirostris, and the melon-headed whale, Peponocephala electra. Two approaches were used. Habitat preferences were investigated by analysing dolphin sighting data and associated physiographical characteristics. Resource partitioning was explored by analysing C and N stable isotopes in skin and blubber biopsies. Only T. aduncus, which showed clear association with coastal habitats in the lagoon, differed from the others in terms of habitat preferences, characterised by shallow depth and slope, and proximity to the coast. All other species shared similar oceanic habitats immediately outside the lagoon, these being of higher depth and slope, greater distance from the coast and were not discernable by discriminant analysis. The two Stenella species and the melon-headed whale displayed very high overlap in habitat physiographic variables. The analysis of stable isotopes confirmed the ecological isolation of T. aduncus and revealed a clear segregation of P. electra compared to the two Stenella that was not apparent in the habitat analysis. This may reflect ecological differences that were not observable from diurnal surface observations.     

基于碳氮稳定同位素技术的小清河口邻近海域底栖食物网结构研究

为了掌握小清河口邻近海域底栖食物网结构特征,于2020年10月在小清河口邻近海域采集沉积物有机质、悬浮颗粒有机物、浮游动物和浮游植物4种潜在食源及35种生物样本,应用碳氮稳定同位素技术以及贝叶斯混合模型(MixSIAR)分析了小清河口邻近海域底栖食物网结构和营养关系.结果显示,潜在食源的δ13C值范围为-25.56‰～...     

浙江三门湾海域主要底上动物生态位及种间联结性

大型底上动物参与海洋生态系统中的物理、化学和生物过程,具有极高的研究价值。浙江三门湾是天然的半封闭海湾,也是海洋生物重要的栖息、觅食和育幼的场所。为探究三门湾海域物种间的资源利用情况及生态关系,在该海域进行了底拖网生物调查。根据2017年和2018年夏季在三门湾海域进行的大型底上生物研究结果,运用优势度(Y)、生态位宽度、生态位重叠、方差比率法(VR)、χ²检验、联结系数(AC)、共同出现百分率(PC)对生态位和种间联结性进行了研究。结果表明: 2017~2018年间三门湾海域共捕获大型底上动物53种,包括两年共有种,即主要底上动物22种。其中优势种3种,包括哈氏仿对虾(Mierspenaeopsis hardwickii)、中华栉孔虾虎鱼(Ctenotrypauchen chinensis)和棒锥螺(Turritella terebra),这三个物种属中生态位种;三门湾主要底上动物依据生态位宽度值划分为3组,即广生态位种、中生态位种和窄生态位种;种对间生态位重叠值总体差异性较大,其与种对的食性、栖息环境密切相关;根据总体联结性分析得主要底上动物总体呈显著正关联,群落结构较为稳定; χ²检验、联结系数(AC)和共同出现百分率(PC)表明种对间联结性较弱,趋近于相互独立。三门湾大型底上动物的群落结构比较稳定,但种对间的关联性在逐渐下降。     

Food and habitat resource partitioning between three estuarine fish species on the Swedish west coast

In 1978 the food and habitat resource partitioning of three small and common fish species, viz. Pomatoschistus microps (Krøyer), Gasterosteus aculeatus (L.) and Pungitius pungitius (L.) were studied in river Broälven estuary on the Swedish west coast (58°22′N, 11°29′E). The area was divided into three habitats, based on environmental features. In July, September, and October stomach contents and size distribution of each species present were analysed.In July there was high food and habitat overlap between the species. Interference interactions probably occurred between some size classes of P. microps and the other two species. P. pungitius was exposed to both intra- and interspecific interactions. In September the food and habitat overlaps between G. aculeatus and P. pungitius were high, while both had low food and habitat overlaps in relation to P. microps. Interactions between G. aculeatus and P. pungitius were probably influenced by more severe abiotic conditions in one habitat, which caused lower abundances there, and higher abundances in the other two habitats. In October no interactions were observed. These results indicate that competition for food at least temporarily determines the species distribution in a temperate estuary, and that estuarine fish populations are sometimes food limited.     

乐清湾秋季虾类群落结构及生态位分析

为探究乐清湾虾类群落结构的形成和影响因素,作者于2020年9月在该海域开展海洋生态系统综合调查,运用相对重要性指数、生态位宽度、生态位重叠等生态指标,结合非度量多维标度法(MDS)和冗余分析(RDA)对群落结构、生态位的重叠和分化进行分析。结果表明:秋季研究海域共有虾类16种,隶属于6科、10属;哈氏仿对虾(Parapenaeopsis hardwickii)和中华管鞭虾(Solenocera crassicornis)为优势种,周氏新对虾(Metapenaeusjoyneri)、脊尾白虾(Exopalaemoncarinicauda)和刀额新对虾(Metapenaeus ensis)为常见种;哈氏仿对虾、中华管鞭虾、周氏新对虾和脊尾白虾属于中等生态位种,其余均为窄生态位种;红条鞭腕虾(Lysmatavittata)与太平洋长臂虾(Palaemonpacificus)的重叠值最高,中国毛虾(Acetes chinensis)、葛氏长臂虾(Palaemon gravieri)和细指长臂虾(Palaemon tenuidactylus)等与其他种类重叠值较低;影响该海域秋季虾类分布的主要环...