Highly reducing sediments are prevalent in seagrass environments. Under anoxic conditions, hydrogen sulfide can accumulate as an end product of anaerobic respiration at levels which may be toxic to halophytes.

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Tissue nutrient content of Gracilaria spp. (Rhodophyta) was tested as a bioindicator of water column nutrient availability in the Logan River and southern Moreton Bay, south-eastern Queensland. Macroalgae were incubated for one to two weeks within flow-through incubation chambers suspended in the water column. Tissue nutrient content of Gracilaria spp, and water column nutrients were measured at five sites over a five-month period.

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Increasing eutrophication of coastal marine environments has led to the development of nutrient sampling programs to monitor water quality. Various shortcomings of chemical analyses have identified the need to develop biological indicators (bioindicators) that can be used to detect available nutrient concentrations. Macroalgal tissue nutrient content, pigments, and amino acids appear to be responsive to water column nutrient availability.

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Macroalgal Nutrient Relationships (Literature Review)

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We measured predation on bay anchovy Anchoa mitchilli eggs and larvae by abundant scyphomedusae Chrysaora quinquecirrha and ctenophores Mnemiopsis leidyi from gut contents, digestion rates, and densities of predators and prey during 9 d in July 1991 at 4 stations in Chesapeake Bay, USA, These predation rates were compared to egg and larval mortality rates measured concurrently in ichthyoplankton surveys.

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Ammonium excretion rates of recently collected specimens of gelatinous zooplankton. the scyphomedusan Chrysaora quinquecirrha DeSor and the ctenophore Mnemiopsis leidyi A. Agassiz, were correlated with body mass and water temperature in measurements made from April to October 1989 and 1990. Rates ranged between 3.5 and 5.0 mug atoms NH4+-N (g dry wt)-1 h-1 for C. quinquecirrha and 3.0 to 4.9 mug atoms NH4-N (g dry wt) -1 h-1 for M. leidyi.

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Assessing Water-Quality with Submersed Aquatic Vegetation

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The phenotypic plasticity and performance of two growth-forms of Caulerpa racemosa (Forsskal) J. Agardh, one found in estuarine conditions, the other growing in a coastal reef environment was studied in laboratory culture. There was no change in the morphology of either growth-form when cultured through a range of salinity (10—40%o) and light (20—140 μEm-2s-1) conditions.

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In this book, the author takes the reader on a delightful natural history tour of the beautiful islands in the Eastern Caribbean Sea. A well traveled natural historian, Professor Marshall unveils a variety of interesting and well communicated vignettes about Caribbean natural history. This book should provide readers with an appreciation of the natural history wonders of the Caribbean region and allow them to become transformed into travelers with an eye for the world around them.

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The relative importance of nitrogen (N) and phosphorus (P) limitation for growth and biomass accumulation in an estuarine population of eelgrass (Zostera marina L.) was examined by in situ additions of nitrogen (+N), phosphorus (+P) and nitrogen plus phosphorus (+N+P) to sediments at low and high loading rates. Nitrogen treatments resulted in no significant increases in leaf tissue N levels and only a small increase in the N content of root plus rhizome tissues.

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