Made available in DSpace on 2014-06-12T18:05:11Z (GMT). No. of bitstreams: 2 arquivo6823_1.pdf: 4586971 bytes, checksum: 716a611f2216f9036e2f438d6997d578 (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2005 / A área estudada compreendeu as praias do Forte Orange, São Paulo, Forno da Cal, Pilar, Jaguaribe e Sossego, na Ilha de Itamaracá. O estudo objetivou conhecer as relações entre os agentes dinâmicos da praia e a fauna intersticial dos sedimentos. No período de novembro de 2003 a outubro de 2004 foram realizadas coletas mensais. As amostras da fauna intersticial foram coletadas no estirâncio, em um quadrado imaginário de 1m x 1m com cinco réplicas coletadas nas extremidades e no centro do quadrado, na baixamar, totalizando 360 amostras. As amostras de sedimentos foram mensais para cada praia e também coletadas no transecto, totalizando 72 coletas. Feituras de perfis de praia foram realizados e seus gráficos confeccionados segundo o referencial absoluto de cada um. A meiofauna esteve composta, segundo a ordem evolutiva por: Nematoda, Rotifera, Tardigrada, Polychaeta, Oligochaeta, Acari, Ostracoda, Copepoda e Mollusca, sendo Nematoda, Copepoda e Oligochaeta representantes da fauna dominante; Polychaeta e Ostracoda como abundante; Rotifera como comum e Tardigrada, Acari e Mollusca como raros. O estudo da distribuição dos sedimentos praiais revelaram a ocorrência do fácies de areias quartzosas fina à média. A morfologia evidencia as praias de São Paulo, Forno da Cal, Pilar, Jaguaribe e Sossego com tendências a processos erosivos e a praia do Forte Orange com tendência deposicional. A variação do balanço sedimentar das praias foi o fator determinante para a composição quantitativa da meiofauna em todo período

Submitted by Fernanda Rodrigues de Lima (fernanda.rlima@ufpe.br) on 2018-10-09T19:28:56Z No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) DISSERTAÇÃO Rodolfo Ferreira Martins do Nascimento.pdf: 1424442 bytes, checksum: b547042e60ca0f385c851cd73be379b8 (MD5) / Approved for entry into archive by Alice Araujo (alice.caraujo@ufpe.br) on 2018-11-21T18:46:28Z (GMT) No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) DISSERTAÇÃO Rodolfo Ferreira Martins do Nascimento.pdf: 1424442 bytes, checksum: b547042e60ca0f385c851cd73be379b8 (MD5) / Made available in DSpace on 2018-11-21T18:46:28Z (GMT). No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) DISSERTAÇÃO Rodolfo Ferreira Martins do Nascimento.pdf: 1424442 bytes, checksum: b547042e60ca0f385c851cd73be379b8 (MD5) Previous issue date: 2015-10-27 / FACEPE / A partir do século XVIII, atividades humanas tais como as emissões de gases de efeito estufa têm se tornado um componente adicional que afeta o sistema climático. De acordo com o IPCC (Painel Intergovernamental de Mudanças Climáticas), a concentração atmosférica desses gases vai continuar a subir. Assim, é esperado um aumento da temperatura média entre 1,4 a 5,8°C até ao final do século 21. O aumento das concentrações de gases de efeito estufa, também podem causar um decréscimo no pH das águas da superfície oceânica de até 0,4 unidades em 2100. Essa alteração de pH, influencia na formação de recifes de corais, animais e algas calcificantes. O objetivo deste trabalho foi avaliar a variação temporal na composição e abundância das famílias de Copepoda Harpacticoida em ambiente natural e em condição experimental de diminuição de pH e aumento de temperatura da água do mar, com as hipóteses de que o aumento da acidez e temperatura da água do mar modifica a estrutura da associação e reduz significativamente a riqueza e equitabilidade de Harpacticoida. Trinta e duas algas (Halimeda sp.) coletadas na Praia de Serrambi – PE foram mantidas em condições laboratoriais de controle e de Cenário de mudança climática, no último sendo alterados o pH e temperatura da água de acordo com previsões para 2100, utilizando aquários preparados para injeção de CO₂ e controle de temperatura. O experimento de laboratório teve duração de 30 dias, sendo realizadas coletas de algas na mesma praia ao início de final do experimento. As algas foram processadas para retirada e identificação dos Copepoda Harpacticoida assim como para análises de clorofila. Foram registradas 17 famílias de Copepoda Harpacticoida. A família Ameiridae foi identificada ao nível específico, sendo encontradas 18 espécies. Os resultados das análises das algas indicaram um efeito significativo do cenário de mudança climática sobre a proporção de clorofilas e aumento da calcificação de Halimeda sp.. Resultados estatísticos mostraram diferenças significativas na estrutura da comunidade de Copepoda Harpacticoida entre a situação controle e o cenário previsto para 2100. A associação de espécies de Ameiridae não apresentou alteração sob condições de mudança climática, um maior tempo de exposição dos animais a condições de acidificação, poderia mostrar resultado significativo para as espécies estudadas, aproximando a família Ameiridae ao resultado obtido para os Harpacticoida. / From the eighteenth century, human activities such as emissions of greenhouse gases have become an additional component that affects the climate system. According to the IPCC (Intergovernmental Panel on Climate Change), the atmospheric concentration of these gases will continue to rise. Thus, it is expected to increase the average temperature of 1.4 to 5.8 ° C by the end of the 21st century. The increase in greenhouse gas concentrations, can also cause a decrease in the pH of ocean surface waters of up to 0.4 units in 2100. This change of pH, influence the formation of coral reefs, animals and calcifying algae. The objective of this study was to evaluate the temporal variation in the composition and abundance of the families of Copepoda Harpacticoida natural environment and experimental condition of decreased pH and increased temperature of sea water, with the hypothesis that the increase in acidity and temperature seawater modifies the structure of the pool and significantly reduces the richness and evenness of Harpacticoida. Thirty-two algae (Halimeda sp.) Collected in Serrambi Beach - PE were kept in laboratory conditions control and climate change scenario, the latter being altered pH and temperature according to forecasts water to 2100, using prepared aquariums for injection of CO2 and temperature control. The laboratory experiment lasted 30 days, algae collections being held on the same beach at the beginning of the end of the experiment. The algae were removed and processed for identification of Copepoda Harpacticoida as well as of chlorophyll analysis. 17 families of Copepoda Harpacticoida were recorded. The Ameiridae family was identified to species level, and found 18 species. The results of the analysis of algae showed a significant effect of climate change scenario on the proportion of chlorophylls and increased calcification of Halimeda sp .. Statistical results showed significant differences in Copepoda Harpacticoida community structure between the control situation and the scenario for 2100. the combination of species Ameiridae showed no change under conditions of climate change, a longer exposure of animals acidification conditions, could show significant results for the species studied, approaching Ameiridae family to the result for Harpacticoida.

No description available.

Submitted by Danielle Karla Martins Silva (danielle.martins@ufpe.br) on 2015-03-12T16:59:05Z No. of bitstreams: 2 Dissertação_Manuelle_Ataide_catalogada.pdf: 2223519 bytes, checksum: 1f7fdcc7b46e96ff802ff2b700eae8ac (MD5) license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) / Made available in DSpace on 2015-03-12T16:59:05Z (GMT). No. of bitstreams: 2 Dissertação_Manuelle_Ataide_catalogada.pdf: 2223519 bytes, checksum: 1f7fdcc7b46e96ff802ff2b700eae8ac (MD5) license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Previous issue date: 2012 / O objetivo do estudo é avaliar o efeito da engenharia de ecossistema causada pelos recifes de Sabellaria wilsoni (Polychaeta: Sabellariidae) na comunidade da meiofauna e na associação de Nematoda na Ilha de Algodoal, Amazônia, Brasil. Dois tipos de recifes arenosos (Cogumelo e Plataforma) bem como o sedimento arenoso circunvizinho de duas praias distintas (terraço de maré baixa e dissipativa) foram estudados. As coletas foram realizadas em junho (estação chuvosa) e dezembro (estação seca) de 2008 em dois perfis perpendiculares à linha de costa em cada local. As amostras obtidas utilizando-se um corer de 3,0cm de diâmetro enterrado até à profundidade de 10cm foram fixadas com formol a 4%, coradas com Rosa de Bengala e triadas em laboratório ao nível de grandes grupos e para o estudo taxonômico foram retirados os 30 primeiros indivíduos de cada réplica. A meiofauna esteve representada por 22 taxa: Acari, Amphipoda, Bivalvia, Cladocera, Copepoda, Cumacea, Gastropoda, Gastrotricha, Hydrozoa, Insecta, Isopoda, Kinorhyncha, Nematoda, Nemertea, Oligochaeta, Ostracoda, Polychaeta, Rotifera, Tanaidacea, Tardigrada, Tunicata e Turbellaria. A densidade média da meiofauna foi de 1774 ind/10cm², sendo Nematoda o táxon dominante em todas as estações e locais. A ANOVA mostrou que dos parâmetros univariados somente a riqueza apresentou diferença significativa entre os ambientes. A PERMANOVA indicou diferenças significativas para as interações entre os ambientes, bem como entre os tipos de recife e praia considerando os ambientes, e interações entre as estações considerando os diferentes tipos de recife e de praia. A associação de Nematoda esteve representada por 2 classes, 9 ordens, 30 famílias, 91 gêneros e 59 espécies. A densidade média da nematofauna foi de 1424 ind/10cm², sendo Daptonema o gênero dominante seguido por Viscosia e Sabatieria. A ANOVA mostrou que dos parâmetros univariados nenhum apresentou diferença significativa entre os ambientes. A PERMANOVA para a nematofauna também indicou diferenças significativas para as interações entre os ambientes, bem como entre os tipos de recife e praia considerando os ambientes, e interações entre as estações considerando os diferentes tipos de recife e de praia. O IndVal, indicou que os gêneros Bathylaimus, Halichoanolaimus, Linhomoeus, Sabatieria e Viscosia são indicadores do ambiente recifal enquanto que Daptonema, Odontophora, Omicronema, Prorhynchonema e Trichotheristus são gêneros indicadores do ambiente praial. Um conjunto de mudanças nos fatores estruturais e abióticos leva à alta diversidade dentro dos recifes indicando a importância de S. wilsoni enquanto engenheiro de ecossistema em ambiente de praia arenosa estuarina no litoral amazônico.

Made available in DSpace on 2014-06-12T15:06:36Z (GMT). No. of bitstreams: 2 arquivo1995_1.pdf: 1694971 bytes, checksum: ec931b1ef5cabc47ff697e28610e6ad5 (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2004 / O presente estudo objetivou determinar a importância da meiofauna como fonte de alimento para os peixes das famílias Gerreidae (Diapterus rhombeus e Eucinostomus sp.) e Gobiidae (Bathygobius soporator e Gobionellus oceanicus). Considerando que os Nematoda constituem o grupo mais representativo da meiofauna no canal de Santa Cruz, Itamaracá PE, investigou-se se poderia existir uma seleção por parte dos predadores. As coletas se processaram em três meses de estiagem e três meses chuvosos em 1998/1999. Foram coletadas 4 réplicas na baixamar com um corer de 2,6 cm de diâmetro e 5,0 cm de comprimento. Os peixes juvenis cujo comprimento padrão do corpo variou de 1,7 a 5,5 cm, foram capturados com rede de arrasto de 1 mm de abertura. A meiofauna dos sedimentos e dos conteúdos gastro-intestinais foi separada através de peneiras com abertura de malhas de 0,044 a 0,5 mm. Cem Nematoda foram retirados das amostras sedimentológicas e todos os indivíduos dos conteúdos para identificação. Foram feitas análises de similaridade para o emprego das ANOSIM, MDS, e SIMPER. Onze táxons foram registrados, apresentando a densidade máxima em janeiro/99 (20.458 ind. 10 cm-2) e a menor em junho/99 (4.162 ind. 10 cm-2). Os táxons mais abundantes foram os Nematoda seguidos dos Copepoda. Os outros demais grupos apresentaram densidades que variaram temporalmente. Os índices de diversidade empregados para a meiofauna e Nematoda dos conteúdos não mostraram grande variabilidade sazonal. O MDS utilizado para correlacionar a meiofauna e aquela correspondente aos segmentos gastro-intestinais mostrou que, possivelmente, os peixes não se alimentam de todos os táxons determinados no ambiente, indicando uma seleção. O SIMPER mostrou que Copepoda e Nematoda são os táxons responsáveis pelo padrão de alimentação, sendo os primeiros os mais abundantes. Um total de 56 gêneros de Nematoda foram registrados no sedimento, sendo que, destes, três foram detectados somente no conteúdo gastro-intestnal dos peixes. Os mais abundantes foram Terschellingia longicaudata, Spirinia septentrionalis, Daptonema sp.1 e Theristus sp.2, tendo sido determinada uma espécie nova para o último gênero citado. A população nematofaunística esteve composta, principalmente por juvenis. A classificação trófica foi composta, principalmente, por comedores seletivos de depósito (1A) no período seco e por comedores de epistratos (2A) no período chuvoso. A ANOSIM indicou haver correlação significativa tanto para a nematofauna e os gerreídeos, como também para os gabiídeos. A equitabilidade acompanhou a diversidade, sendo mínimas em fevereiro. Os peixes estudados apresentaram uma preferência por Copepoda, enquanto os Nematoda, parecem ser um item negligenciado, não existindo preferência por qualquer gênero em particular. No entanto, foi possível concluir que a meiofauna representa um potencial considerável como alimento para níveis tróficos superiores, tendo em vista as altas densidades registradas. De acordo com a quantidade de indivíduos meiofaunísticos detectados no conteúdo gastro-intestinal dos peixes, a meiofauna deve ser compreendida como uma importante fonte energética para peixes juvenis estuarinos

Made available in DSpace on 2014-06-12T23:03:42Z (GMT). No. of bitstreams: 2 arquivo9485_1.pdf: 2203589 bytes, checksum: df85b08456be6ed28739e1289ca0d9ba (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2012 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / O objetivo do estudo é avaliar o efeito da engenharia de ecossistema causada pelos recifes de Sabellaria wilsoni (Polychaeta: Sabellariidae) na comunidade da meiofauna e na associação de Nematoda na Ilha de Algodoal, Amazônia, Brasil. Dois tipos de recifes arenosos (Cogumelo e Plataforma) bem como o sedimento arenoso circunvizinho de duas praias distintas (terraço de maré baixa e dissipativa) foram estudados. As coletas foram realizadas em junho (estação chuvosa) e dezembro (estação seca) de 2008 em dois perfis perpendiculares à linha de costa em cada local. As amostras obtidas utilizando-se um corer de 3,0cm de diâmetro enterrado até à profundidade de 10cm foram fixadas com formol a 4%, coradas com Rosa de Bengala e triadas em laboratório ao nível de grandes grupos e para o estudo taxonômico foram retirados os 30 primeiros indivíduos de cada réplica. A meiofauna esteve representada por 22 taxa: Acari, Amphipoda, Bivalvia, Cladocera, Copepoda, Cumacea, Gastropoda, Gastrotricha, Hydrozoa, Insecta, Isopoda, Kinorhyncha, Nematoda, Nemertea, Oligochaeta, Ostracoda, Polychaeta, Rotifera, Tanaidacea, Tardigrada, Tunicata e Turbellaria. A densidade média da meiofauna foi de 1774 ind/10cm², sendo Nematoda o táxon dominante em todas as estações e locais. A ANOVA mostrou que dos parâmetros univariados somente a riqueza apresentou diferença significativa entre os ambientes. A PERMANOVA indicou diferenças significativas para as interações entre os ambientes, bem como entre os tipos de recife e praia considerando os ambientes, e interações entre as estações considerando os diferentes tipos de recife e de praia. A associação de Nematoda esteve representada por 2 classes, 9 ordens, 30 famílias, 91 gêneros e 59 espécies. A densidade média da nematofauna foi de 1424 ind/10cm², sendo Daptonema o gênero dominante seguido por Viscosia e Sabatieria. A ANOVA mostrou que dos parâmetros univariados nenhum apresentou diferença significativa entre os ambientes. A PERMANOVA para a nematofauna também indicou diferenças significativas para as interações entre os ambientes, bem como entre os tipos de recife e praia considerando os ambientes, e interações entre as estações considerando os diferentes tipos de recife e de praia. O IndVal, indicou que os gêneros Bathylaimus, Halichoanolaimus, Linhomoeus, Sabatieria e Viscosia são indicadores do ambiente recifal enquanto que Daptonema, Odontophora, Omicronema, Prorhynchonema e Trichotheristus são gêneros indicadores do ambiente praial. Um conjunto de mudanças nos fatores estruturais e abióticos leva à alta diversidade dentro dos recifes indicando a importância de S. wilsoni enquanto engenheiro de ecossistema em ambiente de praia arenosa estuarina no litoral amazônico

Areas of hypoxia are found in coastal areas worldwide, and have become increasingly widespread. These areas vary in their duration and dissolved oxygen concentration from occasional diurnal hypoxia, as found in Corpus Christi Bay, Texas, seasonal hypoxia as in the northern Gulf of Mexico, to continuous hypoxia as found in oceanic oxygen minimum zones. The effects of exposure to low dissolved oxygen (DO) depend on the duration of exposure, the DO concentration and an organism’s tolerance to hypoxic conditions. Most studies have focused on lethal effects of hypoxia by comparing the abundance of benthic organisms and the species composition of benthic communities between hypoxic and normoxic areas. Sub-lethal effects of such as changes in reproduction may occur at less severe hypoxic conditions (by definition), but may still have effects at the population level. The goal of this study is to examine the sub-lethal reproductive effects of low DO on harpacticoid copepods. The life-history traits and reproductive biology of meiobenthic harpacticoid copepods make this group of organisms useful as test organisms to measure the sub-lethal effects of hypoxia on reproduction. It is hypothesized that changes in reproductive traits may be observed at DO concentrations higher than those that cause lethal effects because of the high energetic cost of female harpacticoid reproduction which may result in reduced fitness. Laboratory studies were conducted to examine the effects of low DO concentrations on survival, egg production, and the number and size of eggs. Harpacticoid population abundance, biomass and the abundance of ovigerous females were measured from field samples collected across sites that varied in their degree and duration of exposure to low DO. To contrast the effects of hypoxia in environments with different hypoxic exposures, field studies were carried out in the northwestern Gulf of Mexico in an area with near constant summer hypoxia, and in southeast corner of Corpus Christi Bay, Texas which experiences intermittent hypoxia often for less than one hour in the early morning hours during summer. At both field sites total copepod abundance, biomass and the abundance of ovigerous females were reduced at the most hypoxic site type compared the reference sites. In Corpus Christi Bay, total and ovigerous female abundance varied with exposure to hypoxia, but the relative declines in abundance and biomass were less dramatic than in the northern Gulf of Mexico. In the northern Gulf of Mexico, the percentage of ovigerous females within the total harpacticoids collected was reduced (p<0.001) to 3% at the Intermediate and 1% at the Hypoxic sites during the summers, but in the fall of 2007 at all transects had similar percentages (p = 0.81) of ovigerous females which ranged from 13 to 16%. Reference sites had a higher number of families with ovigerous females, and the relative abundances of those families were more evenly distributed at Reference sites compared to Hypoxic and Intermediate transects. Patterns of ovigerous female abundance with respect to DO concentration were similar across numerous harpacticoid families found at the study sites. Harpacticoid copepods in laboratory studies tolerated near anoxic DO conditions for longer than 120 hours. Average survival rates of the harpacticoids Schizopera knabeni and Nitokra affinis during periods of low DO with elevated ammonium concentrations were less than 50%, while survival rates for the other treatments were near 100%. The formation of an egg mass was reduced in the near anoxia treatment, but egg clutches did not form at all in the treatment that combined near anoxia and 10 micromolar ammonium. The DO concentration and presence of ammonium were important factors to the severity of population decline that were illustrated by population estimate calculations. Population estimates based on laboratory measurements of Nitokra affinis resulted in calculations of reduced survival and reproductive rates related to hypoxic exposure greatly decrease the potential population of the group, which may affect the copepod population’s ability to recover from hypoxic events. The effects of hypoxia on harpacticoid copepods are the result of the length of exposure, the concentration of low dissolved oxygen and exposure to other chemical fluxes that increase during periods of hypoxia. The measurement of reproductive indicators, such as the presence of an egg mass and the proportion of ovigerous females in a population, could be used to indicate the adverse environmental effects of low dissolved oxygen exposure. The studies from this dissertation are the first to document reproductive effects of low dissolved oxygen on harpacticoid populations in the field. Laboratory studies within this dissertation indicate the interaction between ammonium and hypoxia on survival and reproduction in harpacticoids. Future studies are needed to further determine the effects of hypoxia on the whole-life cycle of harpacticoid copepods. / text

Meiofauna are an ecologically significant component of marine benthic communities worldwide. Nematodes, in particular, are arguably the most abundant metazoans on Earth and often form highly diverse communities in marine sediments. The study of meiofauna, however, often lags behind that of macrofauna, probably due to the small size of meiofaunal organisms and the paucity of suitably-trained taxonomists or para-taxonomists. Our understanding of basic ecological questions, such as the role of meiofauna in the energetics of benthic communities, as well as the nature and extent of possible relationships between meiofauna and macrofauna in detritus-based communities, is still limited. The present study aimed to address these questions in the context of intertidal seagrass (Zostera muelleri) meadows and adjoining unvegetated sediments in Papanui Inlet, Otago Peninsula. The near absence of taxonomical and ecological studies on free-living marine nematode species in New Zealand also prompted the description of several new species and as well as a comparison of species assemblages from the study sites. Meiofaunal abundance (range: 1325-4979 ind. 10cm�) in the top 5cm of sediments was not significantly different inside and outside the seagrass meadow. Meiofaunal biomass and production estimates were small relative to macrofauna (approx. 1 and 5% of macrofaunal values, respectively), with little variation in both meiofaunal and macrofaunal values between vegetated and unvegetated habitats. Analysis of the isotopic and fatty acid composition of primary producers, sediment organic matter, and consumers at the study sites suggest that a significant proportion of secondary productivity in seagrass meadows is fuelled by macrophyte detritus. These data suggest that secondary productivity in the seagrass meadow was limited by the low palatability of macrophyte detritus compared with microalgal food sources, resulting in lower trophic transfer efficiency in vegetated sediments. These results contrast with previous findings showing a large contribution of meiofauna to the secondary productivity of vegetated sediments, as well as greater secondary productivity inside than outside seagrass meadows. The nature of the sediments (coarse particle size with low organic matter content) is likely to have led to low meiofauna biomass whilst favouring large suspension feeders. The low availability of high quality food sources (i.e. seston, benthic microalgae, and epiphytes) in vegetated sediments may have contributed to the lower than expected secondary productivity inside the seagrass meadow. Most of the dominant nematode species found at the study sites were new to science, and 6 new species were described. Significant differences were found in the nematode assemblages between sites and sediment depths. There was a trend of greater nematode diversity and abundance in vegetated sediments, but this was restricted to the uppermost 2cm of sediments. The effect of seagrass on nematode assemblages is likely to be mediated by the effect of blades on sediment characteristics and the presence of roots. The present study suggests that the presence of Zostera muelleri results in greater biodiversity of sheltered soft-shore communities on a local scale. The addition of ��C-labelled macroalgal detritus (Enteromorpha) to microcosms in a feeding experiment resulted in minimal labelling of harpacticoid copepods and nematodes. Lack of change in the fatty acid composition of the latter also suggests limited assimilation of detritus during the experiment. It is likely that consumers choose benthic microalgae over detritus when both food sources are available in the field. High content of highly unsaturated fatty acids (HUFAs) in nematodes from the field suggests, for the first time, that they are a high quality food source to higher trophic levels. A feeding experiment investigating the effect of bacterivorous nematodes on detritus assimilation rates by amphipods did not support the hypothesis that nematodes increase the trophic transfer efficiency between detritus and macrofaunal detritivores. It is unclear whether amphipods preferentially fed on detritus or whether nematodes escaped predation by burrowing deeper in the sediment. Data obtained in the present study, however, shows that marine bacterivorous nematodes can biosynthesise/accumulate HUFAs in high concentrations despite their low concentrations in their diet. Nematodes could, therefore, provide an important source of these essential nutrients to bulk deposit feeders living in otherwise HUFA-poor sediments.

No description available.

Meiofauna are an ecologically significant component of marine benthic communities worldwide. Nematodes, in particular, are arguably the most abundant metazoans on Earth and often form highly diverse communities in marine sediments. The study of meiofauna, however, often lags behind that of macrofauna, probably due to the small size of meiofaunal organisms and the paucity of suitably-trained taxonomists or para-taxonomists. Our understanding of basic ecological questions, such as the role of meiofauna in the energetics of benthic communities, as well as the nature and extent of possible relationships between meiofauna and macrofauna in detritus-based communities, is still limited. The present study aimed to address these questions in the context of intertidal seagrass (Zostera muelleri) meadows and adjoining unvegetated sediments in Papanui Inlet, Otago Peninsula. The near absence of taxonomical and ecological studies on free-living marine nematode species in New Zealand also prompted the description of several new species and as well as a comparison of species assemblages from the study sites. Meiofaunal abundance (range: 1325-4979 ind. 10cm�) in the top 5cm of sediments was not significantly different inside and outside the seagrass meadow. Meiofaunal biomass and production estimates were small relative to macrofauna (approx. 1 and 5% of macrofaunal values, respectively), with little variation in both meiofaunal and macrofaunal values between vegetated and unvegetated habitats. Analysis of the isotopic and fatty acid composition of primary producers, sediment organic matter, and consumers at the study sites suggest that a significant proportion of secondary productivity in seagrass meadows is fuelled by macrophyte detritus. These data suggest that secondary productivity in the seagrass meadow was limited by the low palatability of macrophyte detritus compared with microalgal food sources, resulting in lower trophic transfer efficiency in vegetated sediments. These results contrast with previous findings showing a large contribution of meiofauna to the secondary productivity of vegetated sediments, as well as greater secondary productivity inside than outside seagrass meadows. The nature of the sediments (coarse particle size with low organic matter content) is likely to have led to low meiofauna biomass whilst favouring large suspension feeders. The low availability of high quality food sources (i.e. seston, benthic microalgae, and epiphytes) in vegetated sediments may have contributed to the lower than expected secondary productivity inside the seagrass meadow. Most of the dominant nematode species found at the study sites were new to science, and 6 new species were described. Significant differences were found in the nematode assemblages between sites and sediment depths. There was a trend of greater nematode diversity and abundance in vegetated sediments, but this was restricted to the uppermost 2cm of sediments. The effect of seagrass on nematode assemblages is likely to be mediated by the effect of blades on sediment characteristics and the presence of roots. The present study suggests that the presence of Zostera muelleri results in greater biodiversity of sheltered soft-shore communities on a local scale. The addition of ��C-labelled macroalgal detritus (Enteromorpha) to microcosms in a feeding experiment resulted in minimal labelling of harpacticoid copepods and nematodes. Lack of change in the fatty acid composition of the latter also suggests limited assimilation of detritus during the experiment. It is likely that consumers choose benthic microalgae over detritus when both food sources are available in the field. High content of highly unsaturated fatty acids (HUFAs) in nematodes from the field suggests, for the first time, that they are a high quality food source to higher trophic levels. A feeding experiment investigating the effect of bacterivorous nematodes on detritus assimilation rates by amphipods did not support the hypothesis that nematodes increase the trophic transfer efficiency between detritus and macrofaunal detritivores. It is unclear whether amphipods preferentially fed on detritus or whether nematodes escaped predation by burrowing deeper in the sediment. Data obtained in the present study, however, shows that marine bacterivorous nematodes can biosynthesise/accumulate HUFAs in high concentrations despite their low concentrations in their diet. Nematodes could, therefore, provide an important source of these essential nutrients to bulk deposit feeders living in otherwise HUFA-poor sediments.