Macroalgal associations of motile epifaunal invertebrate communities on coral reefs     

George Roff  Colette C. C. Wabnitz  Alastair R. Harborne  Peter J. Mumby 《Marine Ecology》2013,34(4):409-419

Small grazing motile epifaunal invertebrates play an important ecosystem role on coral reefs, influencing both the abundance and composition of macroalgal communities and acting as a key food source for a range of predatory fishes. The first aim of this study was to investigate the associations between motile epifaunal communities and four common macroalgal species (Lobophora variegata, Dictyota divaricata, Microdictyon marinum and Halimeda opuntia) on fore‐reef environments in the Exuma Cays (Bahamas, wider Caribbean). Secondly, we investigated the implications of the well documented rise of Caribbean macroalgal cover on invertebrate densities by surveying sites inside and outside the Exuma Cays Land and Sea Park (ECLSP), where increases in parrotfish grazing intensity inside the marine reserves have led to reductions in macroalgal cover. Therefore, surveys compared similar reefs with significantly different macrolagal cover. Comparisons between macroalgal species revealed a four to fivefold difference in motile epifaunal densities per unit volume of macroalgae. Post‐hoc tests revealed that this difference was significant only for Lobophora, with no difference observed among the other species. As macroalgae provide both a refuge from predation and a food source for grazing epifauna, the higher densities of epifauna observed in Lobophora may be attributed to either refuge from visual predators through morphological features (high cover of overlapping blades close to the substrate) or lack of palatability for parrotfish grazing, providing a more stable refuge. Our results revealed no significant differences in diversity, density or community structure of motile epifauna per unit volume of macroalgae between sites inside and outside the ECLSP. Since canopy height and invertivore biomass did not vary systematically across reserve boundaries, this suggests that algal cover does not affect the density of epifaunal invertebrates. However, areal cover was consistently higher for all macroalgal species at sites outside the ECLSP than those inside the reserve. Therefore, when scaled by aerial cover of macroalgae, total abundance of epifauna was twofold higher outside the ECLSP. We suggest that the increasing abundance of macroalgae on Caribbean reefs may be having dramatic effects on epifaunal invertebrate populations and potentially their ecological functions.  相似文献   

Deja vu? A second mytilid mussel,Semimytilus algosus,invades South Africa's west coast     

《African Journal of Marine Science》2013,35(3):307-313

A second marine mussel is shown to have invaded South Africa's west coast. Molecular techniques, based on intraspecific gene sequence divergences, prove its identity as Semimytilus algosus, a member of the family Mytilidae, native to Chile. The identity of an older introduced population found in Namibia is also confirmed. The present geographic range of S. algosus in South Africa extends some 500 km, from Groenriviersmond in the north to Bloubergstrand in the south. Together with Mytilus galloprovincialis, another previously established invasive mussel, S. algosus has become a dominant intertidal organism on wave-exposed rocky shores across this region. Both species are now much more abundant intertidally than either of the indigenous mussels Aulacomya ater and Choromytilus meridionalis, which have become largely confined to sublittoral and sand-inundated habitats respectively. The two invasive mussels display strong spatial segregation, with M. galloprovincialis dominating the midshore and S. algosus blanketing the lower shore. Through a combination of its small size and high abundance, S. algosus is likely to greatly increase food availability for a range of intertidal predators, many of which cannot consume mussels above a threshold size.  相似文献   

Defense by association: Sponge‐eating fishes alter the small‐scale distribution of Caribbean reef sponges          下载免费PDF全文

Michael K. Wooster  Micah J. Marty  Joseph R. Pawlik 《Marine Ecology》2017,38(2)

Recent studies have demonstrated that sponge‐eating fishes alter the community of sponges on coral reefs across the Caribbean. Sponge species that lack chemical defenses but grow or reproduce faster than defended species are more abundant on reefs where sponge‐eating fishes have been removed by overfishing. Does predator‐removal have an effect on the distribution of sponges at smaller spatial scales? We conducted transect surveys of sponge species that are palatable to sponge predators in proximity to refuge organisms that are chemically or physically defended (fire coral, gorgonians, hard corals) on the heavily overfished reefs of Bocas del Toro, Panama, and a reef in the Florida Keys where sponge‐eating fishes are abundant. In Panama, palatable sponge species were not distributed in close association with refuge organisms, while in the Florida Keys, palatable sponge species were strongly associated with refuge organisms. The presence of fish predators alters the meter‐scale pattern of sponge distribution, and defense by association enhances biodiversity by allowing palatable sponges to persist on reefs where sponge‐eating fishes are abundant.  相似文献   

Long-term increase in crustacean zooplankton abundance in the southern Benguela upwelling region (1951-1996): bottom-up or top-down control?     

Verheye  Hans M.; Richardson  Anthony J. 《ICES Journal of Marine Science》1998,55(4):803-807

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Back-calculated individual growth of long rough dab (Hippoglossoides platessoides) in the Barents Sea     

Fossen  I.; Albert  O. T.; Nilssen  E. M. 《ICES Journal of Marine Science》1999,56(5):689-696

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武汉东湖透明薄皮溞的捕食效率     

李纯厚  黄祥飞 《湖泊科学》1993,5(2):159-163

本文在室内模拟自然水温研究了东湖透明薄皮溞（Leptodora Kindti）对优势枝角类短尾秀体溞（Diaphanosoma brachyurum）和微型裸腹溞（Moina micrura）的捕食效率。实验结果表明,在17℃和21℃时透明薄皮溞对短尾秀体溞的捕食率系数（predation rate coefficient）或称滤过率（clearance rate）分别为15.9和18.2mL predator^-1day^-1。17℃时透明薄皮溞对微型裸腹溞的捕食率系数为30.1mL predator^-1day^-1。不同的猎物密度对捕食率系数亦有影响。在17℃,当猎物密度从200ind mL^-1增为800ind mL^-1时,透明薄皮溞对裸腹溞的捕食率系数则从30.1mL predator^-1day^-1下降为15.1mL predator^-1day^-1,对短尾秀体溞的捕食率系数亦从15.9mL predator^-1day^-1降为7.8mL predator^-1day^-1。  相似文献   

Changes in the fish fauna of a tropical Australian estuary since 1990 with reference to prawn predators and environmental change     

S.J.M. Blaber  S.P. GriffithsR. Pillans 《Estuarine, Coastal and Shelf Science》2010

As part of a study of the reasons for declining commercial banana prawn catches in the Weipa area of the Gulf of Carpentaria, and in order to assess whether changes in predator numbers may be a factor influencing prawn numbers, the species composition, numbers and biomasses of fishes in the Embley estuary were re-examined in February 2005 for comparison with the results of a study between 1986 and 1990. The new study duplicated previous methods and used the same sampling sites and the same gear employed during February sampling periods from 1986 to 1990. Overall, the species diversity and catch rates, as well as the numbers of penaeid prawn predators had changed little over 20 years. The overall catch rate for 2005 was 37.4 g m⁻¹ h⁻¹, not significantly different from the overall catch rate of 32.8 g m⁻¹ h⁻¹ (SE 6.6) for the period from 1987 to 1989. The results are discussed in relation to environmental factors and climate change, as well as the substantial declines in prawn catches, which had fallen from over 800 tonnes per annum prior to 1998, to about 70 tonnes per annum.  相似文献   

Predation by estuarine zooplankton on tintinnid ciliates     

J.Roy Robertson 《Estuarine, Coastal and Shelf Science》1983,16(1):27-36

Laboratory experiments were conducted to determine the feeding performances of Uca zoeae and the estuarine copepods Acartia tonsa and Tortanus setacaudatus when these zooplankton preyed upon the co-occurring tintinnids Favella panamensis (length 265 μm) and Tintinnopsis tubulosa (length 148 μm). Predation by Favella on Tintinnopsis was also studied. Over the range of experimental prey densities used, Acartia ingested Tintinopsis at rates linearly related to prey density. Favella was ingested by Aractia at higher rates than was Tintinnopsis. Tortamus ingested Favella more readily than did Acartia, but Tortanus did not ingest Tintinnopsis. Uca ingested both Tintinnopsis and Favella while Tintinnopsis was also ingested by the larger tintinnid Favella. Comparisons of Acartia predation on tintinnids with published data on ingestion of nauplii and phytoplankton showed that when the phytoplankton are dominated by small (diameters < 10 μm) species, tintinnids in concentrations exceeding 10³ organisms 1^?1 can be important items in the diets of Acartia. At lower tintinnid concentrations or when algal species with diameters > 10 μm are present in significant concentrations, tintinnids merely supplement algae in the diet of Acartia. Generally, tintinnids are more important food items for Acartia than are comparably sized nauplii. Only at concentrations exceeding 10⁴ cop. m^?3 can Acartia depress tintinid population growth.  相似文献   

Effects of laughing gull and shorebird predation on the intertidal fauna at Cape May,New Jersey     

M.L. Botton 《Estuarine, Coastal and Shelf Science》1984,18(2):209-220

The intertidal flats of the Cape May, New Jersey shore of Delaware Bay are populated by large numbers of laughing gulls and migrating shorebirds during the spring and early summer. Exclusion of birds from a shallow slough and a sand bar had only minor effects on the infaunal benthic invertebrate assemblage at either site. The Cape May beaches provide a rich source of food in the form of horseshoe crab (Limulus polyphemus) eggs; foraging on this item may be more profitable than probing the sediment for infauna. Gemma gemma, a small, thick-shelled bivalve, composed over 98% of the benthic infauna at both sites in 1980, and this species may be resistant to predation by certain shorebirds, as suggested by Schneider (1978).  相似文献   

Eocene drill holes in cold-seep bivalves of Hokkaido, northern Japan     

Kazutaka Amano  & Robert G. Jenkins 《Marine Ecology》2007,28(1):108-114

Four specimens of the thyasirid Conchocele bisecta (Conrad) and one small specimen of the vesicomyid Hubertschenckia ezoensis (Yokoyama), each with a drill hole made by a naticid gastropod, were found at a cold‐seep site in the upper Eocene Poronai Formation of Hokkaido. This is apparently the oldest record not only of drill holes, but also of predation scars, in a cold‐seep fauna. In addition, drilled vesicomyids are known from several Miocene cold‐seep sites in Japan. We suggest that the Eocene and Miocene chemoautotrophic bivalves were drilled only in the shallow‐water settings preferred by most naticids. The lack of drill holes in Oligocene chemoautotrophic bivalves in the northwestern USA suggests that this innovation, which allowed naticids to prey upon highly toxic bivalves, first appeared in the western Pacific during the Eocene.  相似文献