C, N and P regeneration by a detritivorous fish, Liza haematocheila T. & S.: effects of temperature, diet and body size

Detritus, as a nutrients reservoir, affects the trophic structure and dynamics of communities and supports a greater diversity of species and longer food chains. Detritivorous fish is an important organism to regenerate the nutrients from sediments. Despite the numerous studies on the nutrients cycle in fish, only a few attempts have been made to quantify the regenerating ability. In the present study, we chose the common detritivorous fish redeye mullet as the research object. Redeye mullet is also a common poly-culture fish in China. Diet, including a commercial diet mostly used in aquaculture and a home-made diet with contents close to detritus, was used and considered as a fixed factor. Temperature was also considered as a fixed factor as much research has shown that temperature has significant effects on fish metabolism. Moreover, body size was regarded as a covariate under analysis of covariance. Three key nutrients, namely carbon, nitrogen and phosphorus, were used to measure the nutrient-regenerating ability of redeye mullet under laboratory conditions. The results showed that the nutrient regeneration in percent of the consumption decreased with increasing temperature. Carbon and nitrogen regeneration of redeye mullet fed on commercial diet was lower than those of the home-made diet group, while the opposite was found for phosphorus. In each group, the amount of regenerated nutrients increased linearly with body size. Fed on the home-made diet, 5-g fish at 25 degrees C can regenerate 210.822 mg C, 37.533 mg N and 0.727 mg P per day.

iMarNet: an ocean biogeochemistry model intercomparison project within a common physical ocean modelling framework

Ocean biogeochemistry (OBGC) models span a wide variety of complexities, including highly simplified nutrient-restoring schemes, nutrient–phytoplankton–zooplankton–detritus (NPZD) models that crudely represent the marine biota, models that represent a broader trophic structure by grouping organisms as plankton functional types (PFTs) based on their biogeochemical role (dynamic green ocean models) and ecosystem models that group organisms by ecological function and trait. OBGC models are now integral components of Earth system models (ESMs), but they compete for computing resources with higher resolution dynamical setups and with other components such as atmospheric chemistry and terrestrial vegetation schemes. As such, the choice of OBGC in ESMs needs to balance model complexity and realism alongside relative computing cost. Here we present an intercomparison of six OBGC models that were candidates for implementation within the next UK Earth system model (UKESM1). The models cover a large range of biological complexity (from 7 to 57 tracers) but all include representations of at least the nitrogen, carbon, alkalinity and oxygen cycles. Each OBGC model was coupled to the ocean general circulation model Nucleus for European Modelling of the Ocean (NEMO) and results from physically identical hindcast simulations were compared. Model skill was evaluated for biogeochemical metrics of global-scale bulk properties using conventional statistical techniques. The computing cost of each model was also measured in standardised tests run at two resource levels. No model is shown to consistently outperform all other models across all metrics. Nonetheless, the simpler models are broadly closer to observations across a number of fields and thus offer a high-efficiency option for ESMs that prioritise high-resolution climate dynamics. However, simpler models provide limited insight into more complex marine biogeochemical processes and ecosystem pathways, and a parallel approach of low-resolution climate dynamics and high-complexity biogeochemistry is desirable in order to provide additional insights into biogeochemistry–climate interactions.

Studies on the prevalence of algal blooms along Kerala coast, India

Algal blooms are naturally occurring phenomena in the aquatic environment. These blooms cause mass mortalities of wild and farmed fish and shellfish, human intoxications which sometimes result in death, alteration of marine trophic structure through adverse effects on larvae and other life history stages of commercially important species and death of marine animals. Occurrences of harmful algal blooms and associated mortality have been reported along the coastal waters of India since the early period of the last century. The present study was taken up to study the dynamics of major phytoplankton blooms, which occur along the Kerala coast. The results of quantitative and qualitative analysis of phytoplankton in the coastal waters of Vizhinjam and Chombala, their species diversity and community structure is presented and the major algal blooms recorded along the coast of Kerala during the study period is described and their occurrence is related to the hydrographic and meteorological variations. There is a clear evident from these works in the Indian region that the fishes avoid areas where these harmful algae bloom, either due to the toxicity or due to some irritant property of the chemicals secreted by the algae. Taxonomic diversity studies indicated a change in the community structure of commercial finfishes, crustaceans and molluscs due to the bloom of C.marina and funnel plots indicated the deviation in taxonomic distinctness during the bloom period from theoretical mean for the region.

Sediment fingerprinting as an environmental forensics tool explaining cyanobacteria blooms in lakes

Cyanobacteria (blue-green algae) blooms in water bodies present serious public health issues with attendant economic and ecological impacts. Llyn Tegid (Lake Bala) is an important conservation and amenity asset within Snowdonia National Park, Wales which since the mid-1990s has experienced multiple toxic cyanobacteria blooms threatening the ecology and tourism-dependent local economy. Multiple working hypotheses explain the emergence of this problem, including climate change, land management linked to increased nutrient flux, hydromorphological alterations or changing trophic structure - any of which may operate individually or cumulatively to impair lake function. This paper reports the findings of a sedimentfingerprinting study using dated lake cores to explore the linkages between catchment and lake management practices and the emergence of the algal blooms problem. Since 1900 AD lake bed sedimentation rates have varied from 0.06 to 1.07 g cm−2 yr−1, with a pronounced acceleration since the early 1980s. Geochemical analysis revealed increases in the concentrations of total phosphorus (TP), calcium and heavy metals such as zinc and lead consistent with eutrophication and a rising pollution burden, particularly since the late 1970s. An uncertainty-inclusive sedimentfingerprinting approach was used to apportion the relative fluxes from the major catchment land cover types of improved pasture, rough grazing, forestry and channel banks. This showed improved pasture and channel banks are the dominant diffuse sources of sediment in the catchment, though forestry sources were important historically. Conversion of rough grazing to improved grassland, coupled with intensified land management and year-round livestock grazing, is concluded to provide the principal source of rising TP levels. Lake Habitat Survey and particle size analysis of lake cores demonstrate the hydromorphological impact of the River Dee Regulation Scheme, which controls water level and periodically diverts flow into Llyn Tegid from the adjacent Afon Tryweryn catchment. This hydromorphological impact has also been most pronounced since the late 1970s. It is concluded that an integrated approach combining land management to reduce agricultural runoff allied to improved water level regulation enabling recovery of littoral macrophytes offers the greatest chance halting the on-going cyanobacteria issue in Llyn Tegid.

Características limnológicas e estrutura trófica das comunidades de peixes de alguns lagos naturais e artificiais do Rio Grande do Norte

Artificial lakes must differ from natural lakes in important structural and functional aspects that need to be understood so that these ecosystems can be properly managed. The aim of this work was to test the hypothesis that the artificial lakes (impoundments) in the semi-arid region of the Rio Grande do Norte State are more eutrophic and turbid and have different trophic structure when compared to the natural coastal lakes that occur in the humid eastern coast of the State. To test this hypothesis, 10 natural lakes and 8 artificial lakes with about 100 ha were sampled between September and November 2005 for the determination of some limnological variables and the abundance of the main fish species, which were grouped in three trophic guilds: facultative piscivores, facultative planktivores and omnivores. The results show that the artificial lakes had significantly higher concentrations of total nitrogen, total phosphorus, chlorophyll a , total and volatile suspended solids than the natural lakes. Results also show that the values of pH, total alkalinity, electric conductivity, turbidity as well as the coefficient of vertical attenuation of light were significantly higher in the artificial lakes than in the natural lakes. In the artificial lakes, the abundance of facultative planktivores was significantly higher, while the abundance of facultative piscivores significantly lower than in the natural lakes. There was no significant difference in the abundance of omnivorous fish between the two types of lakes. These results suggest that the increase in turbidity together with the other changes in the water quality of the artificial lakes, modifies the trophic structure of the fish communities reducing the importance of piscivores and the length of the food chains

Efeitos de peixes zooplanctívoros e onívoros sobre a resposta de comunidades planctônicas à fertilização por nutrientes

The food chain theory predict that presence of omnivory prevent the trophic cascade and could be a strong stabilizing factor over resource and consumer community dynamics, and that the nutrient enrichment destabilize populations dynamics. Most of the freshwater tropical reservoirs are eutrophic, and strategies that seek improve the water quality through the control of phytoplankton biomass and nutrient input, become essential for the improvement and preservation of water quality. The aim of this study was test the zooplanktivory (when larvae) and omnivory (when young and adult) effects of Nile Tilapia over the structure and dynamics of plankton communities, in addition or absence of nutrients enrichment. For this, one field experiment was performed with a factorial design 2x3 resulting in six treatments: control, without fish and nutrient (C); with omnivorous fish (O); with zooplanktivorous fish (Z); without fish and with enrichment of nutrients (NP); with omnivorous fish and nutrients (ONP); and, with zooplanktivorous fish and nutrients (ZNP). The two planktivory types reduced the zooplankton biomass and increased the phytoplankton biomass, but the omnivory of filter-feeding fish attenuated the trophic cascade magnitude. The fertilization by nutrients increases the nutrient concentrations in water and the phytoplankton biomass, but the effect on zooplankton is dependent of the trophic structure. In a general way, the effects of the fish and nutrient addition were addictive, but significant interactions among those factors were observed in the answer of some zooplankton groups. The effects of omnivorous fish over the temporal variability of phytoplankton and zooplankton biomass were very variable, the increase or reduce in variability of the plankton depending of the level of nutrients and of the analyzed variable. With base in this study, we conclude that the planktivory type exercised by the fish and the concentrations of nutrients in the water affects the force of pelagic trophic cascades and probably the success of biomanipulation programs for the handling of water quality in lakes and tropical reservoirs

Alimentação dos peixes em um riacho do Parque Estadual Morro do Diabo, bacia do Alto Rio Paraná, sudeste do Brasil

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Análise comparativa da assembléia de aves em dois remanescentes florestais no interior do Estado de São Paulo, Brasil

Realizou-se o levantamento quantitativo e qualitativo da comunidade de aves de dois fragmentos de floresta estacional semidecídua no interior do estado de São Paulo de julho de 2004 a julho de 2005. Para o estudo quantitativo utilizou-se da metodologia de Pontos de Escuta. Foram analisados os índices de diversidade e de freqüência de ocorrência dessa comunidade. O levantamento qualitativo registrou 181 espécies na Fazenda Rio das Pedras - FRP (Itapetininga, 350 ha) e 126 espécies na Fazenda Santa Maria II - FSM (Buri, 480 ha), enquanto que o levantamento quantitativo registrou a presença de 73 espécies em 988 contatos e 64 espécies em 1019 contatos para FRP e FSM, respectivamente. O índice pontual de abundância (IPA) variou de 0,01 (1 contato) a 1,32 (132 contatos), para FRP e na FSM variou entre 0,01 (1 contato) a 0,97 (97 contatos). A diversidade do fragmento da FRP foi de H = 3,04 e na FSM de H = 2,85 onde a eqüitatividade em ambas áreas foi de 0,91. A comunidade de aves nos fragmentos estudados mostrou o mesmo padrão encontrado em outros fragmentos de floresta estacional semidecídua de tamanhos relativos. As categorias alimentares mais representativas nos dois remanescentes foram insetívoras (53% na FSM e 50% na FRP) e frugívoras (23% na FSM e 26% na FRP). Dentre os insetívoros, destacaram-se as famílias Tyrannidae na FSM e Thamnophilidae na FRP. Tanto na FSM como na FRP os insetívoros de sub-bosque foram mais representativos (53% e 51,4% respectivamente), seguidos pelos frugívoros de sub-bosque (50%) na FSM e frugívoros de copa (52,6%) na FRP. A importância do estudo de comunidade de aves esta ligada à elaboração do plano de manejo e conservação das áreas naturais.

Avifauna da Ilha Queimada Grande, SP: diversidade, estrutura trófica e sazonalidade

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Comunidade de aves em um remanescente florestal no Noroeste paulista: estrutura trófica, dinâmica e efeitos da sazonalidade

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

A estrutura trófica da ictiofauna de riachos reflete a estrutura física do habitat?

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Estrutura trófica das assembléia de peixes da represa de Jurumirim, alto rio Paranapanema-SP, Brasil

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Preferência alimentar por insetos aquáticos em espécies de peixes de riacho tropical

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Biologia reprodutiva de populações de peixes em riachos da bacia do rio Itanhaém, litoral sul do estado de São Paulo

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Biologia alimentar da ictiofauna na área de influência do reservatório da usina Mogi Guaçu e lagoas marginais da Estação Ecológica - Fazenda Campininha (SP)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)