Macroalgal blooms affect the food web of tropical coastal ecosystems impacted by fisheries.

Macroalgal bloom events have been frequent in recent years. Eutrophication and overexploitation fishing may favor blooms through nutrient availability and capturing top predators. We aim to investigate the drivers of the macroalgae blooms and their consequences on the food web of the two tropical coastal ecosystems: Porto do Mangue (with high macroalgae production) and Baía Formosa (control environment, without macroalgae), both exploited by artisanal fisheries in northeastern Brazil. The food webs are modeled using the Ecopath with Ecosim (EwE) approach. Our results suggest that fishing did not favor macroalgae blooms but rather the high concentration of nutrients added to the semi-arid conditions. Furthermore, the macroalgae bloom showed low trophic impact, so much of their biomass is transferred into detritus. However, when it decomposes, this accumulation of matter alters the structure and functioning of the ecosystem, affecting its main fish resources: shrimp and piscivorous fish. Investigating blooms is key to management.

Ichthyofauna as bioindicator of environmental quality in an industrial district in the amazon estuary, Brazil.

The objective of the present study was to describe the ecological status of ichthyofauna in an industrial district (Pará river, Amazon estuary), through the use of different environmental descriptors. To evaluate the impacts of the industrial area and cargo terminal, three areas were considered: Zone 1 (maximum impact), Zone 2 (median impact) and Zone 3 (low impact). A total of 77 species were captured. Differences in the composition of the ichthyofauna were recorded between Zones and environments (main channel and tidal channel). The ecological indices revealed clear evidence of the impact of the industrial hub and cargo terminal on the fish communities. In Zone 1, there was a reduction in the number of feeding groups (in the main channel) and larger fish and the Shannon diversity index and Margalef's richness were also significantly lower. The multivariate analysis separated the different Zones clearly into three groups, indicating marked differences in the levels of contamination in the different parts of the study area.

Ichthyofauna as bioindicator of environmental quality in an industrial district in the amazon estuary, Brazil / Ictiofauna com indicador biológico estuarino em um distrito industrial, estuário amazônico, Brasil

The objective of the present study was to describe the ecological status of ichthyofauna in an industrial district (Pará river, Amazon estuary), through the use of different environmental descriptors. To evaluate the impacts of the industrial area and cargo terminal, three areas were considered: Zone 1 (maximum impact), Zone 2 (median impact) and Zone 3 (low impact). A total of 77 species were captured. Differences in the composition of the ichthyofauna were recorded between Zones and environments (main channel and tidal channel). The ecological indices revealed clear evidence of the impact of the industrial hub and cargo terminal on the fish communities. In Zone 1, there was a reduction in the number of feeding groups (in the main channel) and larger fish and the Shannon diversity index and Margalef's richness were also significantly lower. The multivariate analysis separated the different Zones clearly into three groups, indicating marked differences in the levels of contamination in the different parts of the study area.

O objetivo deste trabalho foi descrever o status ecológico da ictiofauna em um distrito industrial (rio Pará, estuário Amazônico), através do uso de diferentes descritores ambientais. Para avaliar o impacto da zona industrial e terminal de cargas, três áreas foram consideradas: Zona 1 (máximo impacto), Zona 2 (médio risco) e Zona 3 (baixo impacto). Um total de 77 espécies foi capturado. Diferenças na composição da ictiofauna foram encontradas em todas as zonas e ambientes (canal principal e canal de maré). Os índices ecológicos revelaram alterações da comunidade de peixes na área do distrito industrial. Na Zona 1 houve uma redução no número de categorias tróficas (no canal principal) e de peixes de grande porte e o índice de diversidade de Shannon e a riqueza de Margalef foram significativamente mais baixos. A análise multivariada separou as Zonas em três grupos, indicando diferenças marcantes no nível de contaminação nas diferentes áreas de estudo.

Fish fauna as an indicator of environmental quality in an urbanised region of the Amazon estuary.

This study describes the biological importance of Guajará Bay (Belém, Pará, Brazil) for fish fauna and presents a diagnosis of water quality in the main channel and creeks, using the icthyofauna as an ecological indicator. A total of 567 individuals from 40 species were identified. About 58% of these use Guajará Bay as a nursery ground, 49 and 81% use the bay as a breeding and feeding ground, respectively. There were no significant differences between environments as measured by the diversity index; however, fish relative abundance (catch per unit of effort) was greater in the creeks than in the main channel. A significant difference was detected in the fish fauna inhabiting the main channel compared with the creeks. In the main channel, icthyofauna significantly differed during December relative to other months.