Ecological distribution of the shrimp Pleoticus muelleri (Bate, 1888) (Decapoda: Penaeoidea) in southeastern Brazil

The abundance and ecological distribution of the shrimp Pleoticus muelleri as a function of certain environmental factors were investigated from January 1998 through December 1999 in the region of Ubatuba, São Paulo, Brazil. The collections were made monthly in the bays of Ubatumirim (UBM), Ubatuba (UBA) and Mar Virado (MV). Each bay was divided into six sampling transects, four transects parallel to the shoreline and two near the rocky shores on the opposite side. We employed a commercial shrimp boat equipped with two double-rig nets. A total of 6252 shrimp were collected, including 3321 from MV, 1467 from UBM, and 1464 from UBA. Most of the shrimp were caught in the deeper, higher-salinity areas. The high abundance of P. muelleri observed in the southern part of the region studied was related to a sediments with a higher percentage of silt and clay. The numbers of P. muelleri were positively correlated with periods of cooler temperatures. Thus, temperature and the type of sediment were determinant factors in the distribution of P. muelleri in this region.     

Seasonal and interannual variation in distribution and population abundance of the shrimp Crangon franciscorum in San Francisco Bay

Shrimp are an important component of the San Francisco Bay biota, both as predators on benthic fauna, and as a food source for predatory fish. Of three common species in the bay, Crangon franciscorum is the most abundant. The bay is predominantly a nursery area for maturing shrimp of this species. During the main reproductive period in the early spring, ovigerous females and planktonic larvae are in most years centered outside the bay in the nearshore ocean, although both are also present in the bay. Juveniles move into both the southern reach and the northern reach shortly after settling, and landward-flowing bottom currents are possibly instrumental in this migration. The seasonal cycle of shrimp abundance in the bay, dominated by this spring immigration of newly settled juveniles, is characterized by a progressive migration of the growing shrimp up the estuary coincident with upstream penetration of higher salinity water during summer. Differences in abundance and distribution between the years 1980, 1981, and 1982 suggest that the level of river discharge and accompanying salinity regime are important controlling factors in the distribution, recruitment levels, and subsequent survival and growth of C. franciscorum in the San Francisco Bay.     

Importance of predation by white shrimp Litopenaeus setiferus on estuarine subtidal macrobenthos

Macrobenthic invertebrates are an important food source for higher trophic levels in freshwater and marine habitats, yet the importance of predation impacting regular seasonal changes in macrobenthos abundance remains unclear. Benthic invertebrates and transient marine species in temperate estuaries display inverse patterns of seasonal abundance, suggesting a link between predation and summer macrobenthos abundance minima. We conducted manipulative caging experiments to test the importance of predation by white shrimp (Litopenaeus setiferus) in regulating estuarine subtidal macrobenthos densities. We predicted greater declines in macrobenthos densities with increased shrimp densities due to predation rather than disturbance and macrobenthos emigration. Using these field and laboratory data, we estimate whether white shrimp predation can significantly contribute to the macrobenthos seasonal abundance minima observed in long-term monitoring data.White shrimp predation was measured in the field using 7-d predator enclosure/exclusion experiments. Within the uppermost 0-2 cm of sediment, total macrobenthos densities decreased within shrimp enclosure cages using 12 or 36 shrimp m^− 2. Laboratory experiments distinguished between the effects of shrimp predation versus shrimp disturbance and macrobenthos emigration. Shrimp predation significantly reduced macrobenthos densities, while effects of shrimp disturbance and macrobenthos emigration were not significant in these experiments. Despite the impacts from other ambient predators and other abiotic factors, white shrimp were clearly capable of driving subtidal macrobenthos from their annual maximum density in winter/spring to their summertime minimum density.     

Seasonal dynamics and grazing rate of zooplankton in Yueqing Bay, China

The species composition, biomass, abundance, and species diversity of zooplankton were determined for samples collected from August 2002 to May 2003 from 14 stations in Yueqing Bay, China. Phytoplankton growth rate and microzooplankton grazing rate were obtained by using the dilution method developed by Landry and Hassett. The spatial and temporal variations of zooplankton and its relationship with environmental factors were also analyzed. The results showed that the zooplankton in the Yueqing Bay could be divided into four ecotypes, namely coastal low saline species, estuary brackish water species, offshore warm water species, and eurytopic species. A total of 75 species of zooplankton belonging to 56 genera and 17 groups of pelagic larva were identified in the Yueqing Bay. The coastal low saline species was the dominant ecotype in the study area, and the dominant species were Labidocera euchaeta, Acartia pacifica, Acrocalanus gibber, Pseudeuphausia sinica, and Sagitta bedoti among others. There was considerable seasonal variation in zooplankton biomass and abundance in the surveyed areas. The peak biomass appeared in August, descending in November and in May, and the lowest biomass appeared in February. Similarly, the highest abundance of zooplankton was observed in August, with the abundance descending in the following months: May, November, and February. There were similar horizontal distribution patterns for the biomass and the abundance of zooplankton. They both increased from the upper to the lower bay in February and May, but decreased from the upper to the lower bay in August. Biomass and abundance were evenly distributed in the Yueqing Bay in November. Moreover, there was marked seasonal variation in the species diversity of zooplankton, which conformed to the abundance of zooplankton. Results of the dilution experiments indicated that there was grazing pressure of microzooplankton on phytoplankton in the Yueqing Bay throughout the year though the rate of microzooplankton grazing on phytoplankton varied seasonally. Phytoplanktons were growing at 0.26–2.07/d and grazed by microzooplankton at a rate of 0.15–0.48/d in different seasons. __________ Translated from Acta Ecologica Sinica, 2005, 25(8): 1853–1862 [译自: 生态学报, 2005, 25(8): 1853–1862]     

Intrabasin variation in allometry coefficients of Lenkoran Capoeta capoeta gracilis (Keyserling, 1861) in the Gorganroud basin,southeast Caspian Sea,Iran

It is believed that streams of a basin may contribute to stream‐specific variation in allometry coefficients related to between‐habitat differences. To test intra‐basin variation of the allometry coefficients of Lenkorn Capoeta capoeta gracilis (Keyserling, 1861), a total of 1731 individuals were sampled in six streams of the Gorganroud basin (southeast Caspian Sea) between April and May 2008. Values of b ranged from 2.647 for males of Chelchai to 2.964 for females of Madarsou, indicating negative allometric growth for the fish in the basin. There were variations in the allometry coefficient among the considered groups, which can be interpreted as species’ response to different habitats. To the best knowledge of the authors, this study documents the comparative reference on variation of allometry coefficient of Capoeta capoeta gracilis in southeast Caspian streams.     

The predatory role of white shrimp (<Emphasis Type="Italic">Litopenaeus setiferus</Emphasis>) in seasonal declines of subtidal macrobenthos

The overall purpose of this study was to develop a quantitative model to assess the influence of L. setiferus predation on subtidal macrobenthic abundance cycles in an estuarine creek system. Subtidal macrobenthic populations in temperate marine soft-bottom environments are known to undergo seasonal abundance cycles. Although the factors responsible for driving these seasonal shifts in abundance are difficult to identify, both environmental and biological factors have received credit. Juvenile white shrimp (Litopenaeus setiferus) are seasonally abundant epibenthic predators in the North Inlet estuary that have significant influence upon estuarine macrobenthic densities. Data generated from field and laboratory studies were combined with 20 years of long-term monitoring data to simulate seasonal variations in macrobenthos abundance under different levels of L. setiferus predation. Model simulations generated clear reductions in subtidal macrobenthos densities, confirming the role of L. setiferus as major consumers of macrobenthos. Model uncertainty was small, and model accuracy increased with shrimp density. In years with low or medium shrimp densities, predicted macrobenthos densities tended to be higher than those observed, yet predicted rates of decline still paralleled long-term observations. Model simulations best matched observed data for the representative high shrimp density year tested. Results indicate that variability in multiple factors, including L. setiferus predation, likely control macrobenthos abundance cycles. Predation by earlier-arriving epibenthic feeders may drive initial macrobenthos declines earlier in the year, with L. setiferus predation then intensifying and extending these declines throughout the summer and fall. This modeling approach is an important step toward understanding the role of multiple factors driving seasonal macrobenthos dynamics, and the L. setiferus population was tractable for examining the importance of epibenthic predation on these organisms. Handling editor: Luigi Naselli-Flores     

Diet and foraging opportunism of the Guiana dolphin (Sotalia guianensis) in the Abrolhos Bank,Brazil

Diet analysis allows exploring how coastal dolphins interact with the environment and their role in the marine food webs. We studied the diet and feeding ecology of the Guiana dolphin, Sotalia guianensis, through analysis of stomach content from 42 animals stranded on the eastern coast of Brazil. A total of 1,336 semidigested prey items (fish, otoliths, cephalopod beaks, and crustaceans) were identified. Teleost fish comprised the most frequent food item (92% of the total), followed by cephalopods, and crustaceans. Prey belonged to 34 taxa and richness in individual stomachs varied from 1 to 15 prey taxa. Prey were generally small, but showed a significant trend to increase in size with dolphin length. The main prey of Guiana dolphins were demersal, estuarine, and sound-making fish such as catfish and sciaenids. No sex-related differences in diet were found. Diet composition varied seasonally and occurrence of prey items was coherent with breeding or high abundance periods of some fish species and squids. Our study shows the importance of demersal prey from estuarine and soft-sediment habitats to Guiana dolphin in the Abrolhos Bank and reveals that feeding habits are generalist and opportunistic, with diet reflecting the seasonal abundance and availability of prey.     

Nursery ground value of an endangered wetland to juvenile shrimps

Although urban development impacts wetlands around the world, until now there have been no studies of its effects on coastal wetlands in tropical regions of developed countries such as Australia. In fact the ecological value of such wetlands is poorly understood. This study provides an initial step in evaluating the ecological value of urbanised, tropical coastal wetlands by determining (a) the extent to which a remnant wetland, in a highly urbanised estuary in northern Australia, is used by juvenile commercial penaeid shrimps, and (b) the extent to which the shrimps rely on food chains based on wetland plants versus marine based food chains. Juvenile penaeids were abundant in the 11 wetland pools sampled. Catches included 5 commercial penaeids with two species, Fenneropenaeus merguiensis and Metapenaeus bennetae, comprising half the catch. Densities in the wetland pools were usually substantially higher than in adjacent estuarine habitats. Stable isotope analysis indicated that much of the nutrition of juvenile shrimps was supplied by marine primary producers (phytoplankton, epiphytic and epilithic algae, microphytobenthos, green filamentous algae) however the locally abundant saltmarsh grass Sporobolus virginicus was also a major contributor. In contrast, there was little indication of nutritional support from mangrove carbon. The lack of importance of mangrove carbon is surprising because the catches of F. merguiensis are often closely linked to the area or extent of mangroves, suggesting that aspects of mangrove systems other than the supply of mangrove carbon may determine the distribution of juvenile F. merguiensis.     

Distribution and biology of marine cladocerans in the coastal waters of southern China

Geographical and seasonal distributions of marine cladocerans in the coastal waters of southern China were studied. Penilia avirostris was the most common species, followed by Evadne tergestina and Podon schmackeri. P. avirostris and E. tergestina were most common during summer. P. schmackeri, found only in a small bay northeast of Hong Kong, showed no clear seasonal pattern of occurrence. P. avirostris and E. tergestina were found at temperatures ranging from 16–32°C and salinity ranging from 7.3–37.2. P. schmackeri was restricted to a temperature range of 17–29°C and a salinity range of 31.0–37.2. No significant relationships between marine cladoceran abundance and chlorophyll a concentration were found in samples taken from Tolo Harbour. Parthenogenetic brood size of P. avirostris and E. tergestina ranged from 1 to 14, while P. schmackeri was found to carry up to 19 embryos per brood. No geographical trend in fecundity patterns was observed. No correlation was found between body length and brood size. The occurrence of females with resting eggs was rare.     

Ecological distribution of Penaeus schmitti (Dendrobranchiata: Penaeidae) juveniles and adults on the southern coast of São Paulo state,Brazil

This study aimed to describe the ecological distribution and the effects of environmental factor oscillation on the life cycle of Penaeus schmitti along the coastal area of Cananéia, southern São Paulo state, Brazil. Shrimp and environmental factors were sampled monthly from July 2012 to May 2014 at seven sampling stations covering both estuarine and marine environments, using a shrimp fishing boat. A total of 273 juveniles and 829 adults were sampled, and there were significant differences in body size (carapace length – CL) throughout the seasons (ANOVA). Smaller animals were observed in the summers of 2013 and 2014 and at sites closer to the coast, which are under estuarine influence. Adults were observed mostly in autumn and in deeper regions. We detected a positive relationship between the abundance of juveniles and the bottom water temperature and between the abundance of adults and the water salinity (canonical correspondence analysis). The presence of smaller individuals in the estuarine environment demonstrates the importance of the estuaries in this species’ ontogeny, mainly concerning their protection, since this environment has physical (depth) and physiological (salinity) barriers to their predators. Furthermore, we could clearly observe the plasticity of juveniles in relation to environmental factors. In contrast, adults were less tolerant to the variation in environmental factors, mainly water salinity, which was a limiting factor of their distribution. Seasonal differences in body size could be directly associated to this species’ life cycle and characterized by trophic and reproductive migratory activities between the estuarine and oceanic regions.     

Isolation and characterization of microsatellites in three overexploited penaeid shrimp species along the Brazilian coastline

Most Brazilian commercial species of penaeid shrimp are currently overexploited. Thirteen polymorphic microsatellite loci herein isolated and characterized in Farfantepenaeus brasiliensis, Rimapenaeus constrictus and Xiphopenaeus kroyeri could be very useful for population studies on these penaeid species and proved to be potentially functional in cross-amplification with other species of shrimp. These microsatellites may be very helpful tools for research programs aimed at the sustainable management and conservation of these important fishery resources.     

Does the flatfish community of the Mondego estuary (Portugal) reflect environmental changes?

Temporal and spatial patterns of abundance of the flatfish community in the Mondego estuary were investigated from 2003 to 2007, based on monthly beam trawl samples. During the study period there was a severe drought, with consequential reductions in river runoff. A total of eight flatfish species occurred within the estuary, with seasonal specific richness and abundance varying considerably. It was possible to identify three main groups: one composed of species present throughout the study period and in high densities: Platichthys flesus and Solea solea (maximum densities 3.7 and 4.1 Ind 1000 m^?2, respectively); a second group of less abundant but regularly present species: Scophthalmus rhombus and Solea senegalensis (maximum densities 0.2 and 0.3 Ind 1000 m^?2, respectively); and a third group of occasional species that occurred only during the drought period: Arnoglossus laterna, Buglossidium luteum, Dicologlossa hexophthalma and Pegusa lascaris. Flatfish distribution patterns varied according to the estuarine use guild: marine‐estuarine dependent fish occurred mainly in the upper reaches, while marine stragglers and marine‐estuarine opportunists occurred mostly in the downstream areas. Species with more northern latitudinal affinities were the most affected by the drought, related with a lesser extent of river plumes to the coastal area, resulting in a reduction in half of the abundance levels. However, flatfish species with more southern affinities increased in abundance during the drought, benefiting also from an increase in estuarine water temperature. Early summer salinity and precipitation values were good proxies for estimating abundance levels of P. flesus and S. solea, respectively, emphasizing the importance of hydrodynamics for the recruitment and abundance of these commercially important species.     

Seasonal dynamics of a glycan-degrading flavobacterial genus in a tidally mixed coastal temperate habitat

Coastal marine habitats constitute hotspots of primary productivity. In temperate regions, this is due both to massive phytoplankton blooms and dense colonisation by macroalgae that mostly store carbon as glycans, contributing substantially to local and global carbon sequestration. Because they control carbon and energy fluxes, algae-degrading microorganisms are crucial for coastal ecosystem functions. Environmental surveys revealed consistent seasonal dynamics of alga-associated bacterial assemblages, yet resolving what factors regulate the in situ abundance, growth rate and ecological functions of individual taxa remains a challenge. Here, we specifically investigated the seasonal dynamics of abundance and activity for a well-known alga-degrading marine flavobacterial genus in a tidally mixed coastal habitat of the Western English Channel. We show that members of the genus Zobellia are a stable, low-abundance component of healthy macroalgal microbiota and can also colonise particles in the water column. This genus undergoes recurring seasonal variations with higher abundances in winter, significantly associated to biotic and abiotic variables. Zobellia can become a dominant part of bacterial communities on decaying macroalgae, showing a strong activity and high estimated in situ growth rates. These results provide insights into the seasonal dynamics and environmental constraints driving natural populations of alga-degrading bacteria that influence coastal carbon cycling.     

Population demographics of Palaemon peringueyi (Macpherson 1990) (Decapoda: Palaemonidae) in a small intermittently open Eastern Cape estuary

The population demographics of the caridean shrimp Palaemon peringueyi was investigated monthly at four sites over a period of one year in the small, intermittently-open Grants River Estuary situated on the south-east coastline of southern Africa. Mean total abundance and biomass of P. peringueyi ranged between 0 and 23.2 ind m^?2 and 0 and 2.3mg wwt m^?2, respectively. A peak in its abundance coincided with a breaching event that occurred in December 2004, and could be attributed to the mass recruitment of juveniles (carapace length <9mm) into the estuary. Minor peaks in abundance were also associated with marine waters overtopping the sandbar that separates the estuary from the marine environment. The highest biomass values were recorded when the estuary was separated from the sea. Maximum abundance and biomass values of P. peringueyi were generally recorded in the middle reaches of the estuary where extensive beds of submerged vegetation, mainly Potamogeton pectinatus, predominated. Pearson correlation analysis indicated that the total abundance of P. peringueyi was significantly correlated (r = 0.49; p < 0.05) to percentage cover of submerged vegetation. The spatial pattern in abundance and biomass values of the shrimp is thought to reflect the availability of refuge areas against predation. A distinct spatial pattern in the community structure of the shrimp was evident, with juveniles numerically dominating the samples in the lower reaches of the estuary, while mature females predominated in the upper reaches of the system. In the middle reaches, the community comprised both juveniles and adults.     

Diversity and composition of macrobenthic community associated with sandy shoals of the Louisiana continental shelf

Along the Louisiana, USA continental shelf, sandy shoals are shallow, possibly oxygen-rich “islands” surrounded by deeper muddy deposits prone to hypoxia. Shoals also contain significant quantities of fine sand that may be mined in the future for coastal restoration. The ecological role of shoals remains poorly understood and we hypothesized that shoals provide critical habitat for benthic invertebrates. Using Ship Shoal as a model system, we assessed the diversity and structure of macrobenthic assemblages and how community structure varies with season and environmental parameters. High biomass (averaging 26.7 g m⁻²) and high diversity (161 species) of macrobenthos was found in 2006. Polychaetes (45%—72 species) and crustaceans comprised most of the species (28%—46 species); spionids and amphipods dominated the polychaete and crustacean groups respectively, both in terms of number of species and abundances. Sharp decreases in diversity, abundance and biomass occurred from spring to autumn. Species diversity and total abundance significantly increased with decreasing sediment grain size and increasing bottom water dissolved oxygen. Across seasons, mole crabs Albunea paretii and amphioxus Branchiostoma floridae typified the community and contributed most of the biomass. The polychaetes Nephtys simoni, Neanthes micromma, Dispio uncinata, Mediomastus californiensis and Magelona sp. A, the amphipod Acanthohautorius sp. A and the burrowing shrimp Ogyrides alphaerostris also contributed to variation in community composition. Cluster analyses quantified seasonal variation, mainly based on sharp decreases in abundance, as well as spatial differences in species composition oriented along both east–west and north–south gradients. Variation in benthic assemblages was correlated with water depth and sediment characteristics (mean grain size and percentage of gravel-sized shell debris). We conclude that Ship Shoal is an unrecognized biodiversity hotspot and a hypoxia refuge compared to the immediate surrounding area where the benthic community is affected by seasonal hypoxia events and we discuss how sand-mining may influence this community.     

Prawn community structure in the subtropical Mfolozi–Msunduzi estuarine system,KwaZulu-Natal,South Africa

The life cycles of many marine and freshwater prawn species are closely associated with estuarine habitat. Here, the prawn community of the Mfolozi–Msunduzi estuarine system is described and the system's potential as an alternative nursery for prawns during prolonged closure of the adjacent St Lucia estuarine system is examined. Sampling was conducted at five localities in summer and winter in 2007–2012. The Mfolozi–Msunduzi Estuary is a river-dominated system with mouth condition, sediment grain size and turbidity being the most important factors affecting the structure of its prawn community. Twelve prawn species were recorded, including five marine penaeid and five freshwater palaemonid species. The prawn community was numerically dominated by freshwater Macrobrachium equidens and two penaeids, Fenneropenaeus indicus and Metapenaeus monoceros. Significant differences were recorded between summer and winter samples, with freshwater species dominating the catch in summer, while penaeid species were dominant in winter. The marked seasonal change in the prawn community was related to strong river flows during summer creating low-salinity conditions, unsuitable for penaeid postlarval development, throughout most of the system. Compared to St Lucia, the Mfolozi–Msunduzi Estuary can be regarded as a poor alternative nursery area for penaeids during the summer peak postlarval recruitment period.     

Seasonal patterns of primary colonization by lignicolous marine fungi in Hong Kong

During a 14-month investigation of the seasonal pattern of primary colonization by lignicolous marine fungi in the coastal waters of Hong Kong, a pine block (Pinus massoniana Lamb.) was submerged each month at each of the five stations and recovered in the following month. Thirty-eight species of fungi were isolated, three of which were not identified. In this first recorded attempt to describe fungal colonization on submerged blocks quantitatively, five species (Periconia prolifica, Cirrenalia macrocephala, Ceriosporopsis halima, Trichocladium achrasporum and Halosphaeria quadricornuta) were the most frequent and most abundant fungi on the monthly blocks. Statistical analyses of seasonal abundance of these fungi are presented and their occurrence in relation to varying temperature and salinity throughout the year, including the Phoma pattern, are discussed.     

Top–down control by great blue herons Ardea herodias regulates seagrass‐associated epifauna

Top predators can influence the structure and function of plant and animal communities. In coastal marine systems, fish, shark and mammal population declines are major drivers of recent ecosystem‐level change. Cascading effects of predatory wading birds, however, are less understood, even though wading bird populations have declined in many regions. We quantified the effects of predation by the piscivorous great blue heron Ardea herodias fannini on fish, invertebrates and epiphytes living in eelgrass Zostera marina. We found that herons forage on benthic fish in seagrass meadows, and foraging intensity increased from late spring until midsummer. When we experimentally excluded herons, benthic fish abundance increased, and the invertebrate assemblage shifted to more shrimp‐dominated assemblages while grazing gammarid amphipod abundance declined. These shifts were associated with reduced epiphyte abundance when herons were excluded, reflecting a four‐level trophic cascade and mediated by shifts in the grazer assemblage. In summary, we found that a piscivorous wading bird species exerts top down control in a subtidal seagrass ecosystem. Losses and recovery of wading birds could have ecosystem‐level ecological consequences that may need to be considered in the context of concern for overfishing and predator recovery in marine coastal management.     

象山港春、夏季大中型浮游动物空间异质性

为探明象山港大中型浮游动物空间分布特征及主要影响因素,分别于2010年4月、7月大、小潮期对浮游动物群落和相关环境因子进行调查。四个航次共检出浮游动物成体14大类64种、浮游幼体10大类14种,春、夏季群落结构差异极显著(P=0.001),物种更替率为66.7%,优势种差异明显,共同优势种仅有短尾类溞状幼虫(Brachyura zoea)和仔鱼(Fish larvae)两类幼体;同一季节大、小潮物种相似度约为60%,群落结构差异较小(P=0.031);春季生物量和丰度高于夏季,但物种多样性低于夏季。温度是浮游动物群落季节变化的主导因素。方差分析、聚类和多维尺度分析显示:浮游动物群落空间异质性分布方式受潮流影响,群落结构在大潮期梯度分布特征明显,小潮期通常呈斑块性分布;生物量、丰度和多样性等参数的空间分布取决于群落的分布特征,并受影响于该参数在狭湾口内外的差异。典范对应分析及环境参数统计分析表明:梯度分布主要由盐度、悬浮物的梯度性特征决定;主导斑块性分布的因素多样,不同情况下可能为水深、叶绿素a、营养盐和内外水团相互作用;梯度性和斑块性分布均受到潮流影响。总体来看,象山港浮游动物空间分布主要受水文因素控制,受化学和生物因素影响较弱,其中叶绿素a浓度仅在春季与浮游动物丰度有一定相关性,溶解氧、酸碱度和营养盐等水质参数对浮游动物空间分布几乎无直接影响。