Environmental Gradients

Barletta, M.; Dantas, David Valença

doi:10.1007/978-94-017-8801-4_136

Cited by 9 publications

(8 citation statements)

References 13 publications

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“…"An ecocline represents a boundary of progressive change between two systems, representing the response to the gradual difference in one major environmental factor acting at a different scales and influencing the total differences within the gradient" (Attrill and Rundle, 2002). Within any estuarine system, the salinity is the major environmental factor referred in the ecocline concept (Barletta and Dantas, 2016). Hence, researchers have proposed that the proper management of estuaries are dependent upon reliable biological and abiotic data encompassing multiple aspects of space and seasonality along the estuarine gradient (Machado et al, 2016;Barletta et al, 2017a;Underwood et al, 2017).…”

Section: Discussionmentioning

confidence: 99%

Systematic Review of Fish Ecology and Anthropogenic Impacts in South American Estuaries: Setting Priorities for Ecosystem Conservation

Barletta

Lima

2019

Front. Mar. Sci.

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Research on estuarine ecology in South America (SA) increased quali-quantitatively since the early 1980 in search of consistent recommendations for estuarine conservation. The most important ecological theory achieved is that the seasonal fluctuation of the salinity gradient creates an ecocline influenced by gradual changes between river-dominated to marine-like waters. Estuarine fish fauna adapts to these changeable abiotic characteristics, including the spatial, and seasonal bioavailability of dissolved oxygen and numerous pollutants. However, studies on the influence of the estuarine ecocline are still missing for key estuarine systems. This study provides an overview of fish ecology and anthropogenic impacts within estuarine systems of SA and discusses priorities for environmental conservation. Research on fish reached important conclusions regarding essential habitats and fish interaction with other biological and abiotic compartments over spatio-temporal settings, including conditions of severe anthropogenic impacts. These impacts are related to unplanned urban settlements, industrial estates, ports, damming of major rivers, dredging activities, and deforestation for extensive farming. Changes in estuarine morphology alter natural flows and lead to habitat losses, disrupting the ecocline and impairing fishes from moving among formerly connected habitats, especially earlier ontogenetic phases. In addition, industrial, urban, and farming activities often result in high loads of metals and persistent organic pollutants, organic enrichment and oxygen depletion. Moreover, plastic debris, a ubiquitous contaminant with sources on every human activity, including fishing, when fragmented into microplastics, become preferably concentrated in semi-enclosed environments, as estuaries. Metals, POPs and microplastics are actually asserted to be persistent. When in high concentrations, they become bioavailable to the estuarine trophic web through bioaccumulation, being biomagnified or biotransfered toward higher trophic level organisms, such as top predator fishes. Therefore, research on environmental quality and fish ecology must be based on robust sampling designs along the whole ecocline using long-term approaches. In addition, basic sanitation, co-management, an improved Barletta and Lima Ecology and Conservation of South American Estuaries licensing system and scientifically-based risk assessments/monitoring for all sorts of enterprise are also urgent. These conservation priorities need to be in place before human-driven changes surpass the ecosystem's capacity to produce resources and maintain services.

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Section: Discussionmentioning

confidence: 99%

Systematic Review of Fish Ecology and Anthropogenic Impacts in South American Estuaries: Setting Priorities for Ecosystem Conservation

Barletta

Lima

2019

Front. Mar. Sci.

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“…The estuary is located in a tropical area (Barletta and Costa, 2009;Costa et al, 2017), which favoured high water temperatures throughout the year. This factor can affect the dissolution of gases as oxygen in the water, decreasing their availability for biological and chemical processes (Yin et al, 2004; Harrison and Whitfield, 2006; Kong and Ye, 2014;Wu et al, 2016).Salinity variations defined the estuarine gradient (Attrill and Rundle, 2002;Barletta and Dantas, 2016). In 2006, the dry season was very severe (33.9 ± 8.5 mm), decreasing freshwater entering the estuary and significantly increasing salinity locally, with the greatest marine influence on the estuary of all years, similarly to other reports in the literature (Yin et al, 2004).…”

Section: Discussionmentioning

confidence: 99%

“…Water temperature and salinity are important abiotic variables, which together play a fundamental role in the distribution of aquatic biota, with the determination of ecoclines (Attrill and Rundle, 2002;Yin et al, 2004;Harrison and Whitfield, 2006;Nejrup and Pedersen, 2008;Barletta and Dantas, 2016;Dolbeth et al, 2016). Sudden and/or large changes in these parameters may compromise environmental quality over time, as may change the composition and distribution of biota (Lucena-Moya and Duggan, 2017; Paul and Calliari, 2017), alteration of areas of high ecological importance considered nurseries (Barletta et al, 2005;Blaber, 2013), increase the effect of organic pollution on estuaries as well as the distribution of plastics and microplastics (Possatto et al, 2011;Ivar do Sul and Costa, 2013;Ivar do Sul et al, 2014;Lima et al, 2014), dilution of effluents (Govindasmy and Chandrasekaran, 1992;Uriarte and Villate, 2004;Whitehead et al, 2009;Telesh and Khlebovich, 2010), and absorption and accumulation of pollutants by biota (Tett et al, 2003;Roselli et al, 2013;Zhou et al, 2017).…”

Section: Discussionmentioning

confidence: 99%

“…According to Kjerfve (1990), the main axis of an estuary can be sectioned into large compartments or areas-upper, middle, and lower-considering its morphology and salinity, since riverine environments down to adjacent coastal areas. Each section of the main channel is an habitat (Barletta et al, 2005;Lima et al, 2014), with different biogeochemical behaviour, plant and animal communities, giving rise to an ecological gradient (Attrill and Rundle, 2002;Barletta and Dantas, 2016). Composed of a combination of rivers, streams, ponds, tidal channels, islands, wetlands and flooded mangrove forests, this estuary accommodates a diverse aquatic fauna (fish, molluscs, crustaceans) ( Barletta and Costa, 2009;Dantas et al, 2010;Lima et al, 2014) with high conservation, social and economic importance.…”

Section: Study Areamentioning

confidence: 99%

“…These ecosystems are in a transitional range between the fluvial and marine environments, influenced by the maritime amplitude, which causes a marked variation of its environmental parameters, such as nutrients and salinity (Kennish, 1991(Kennish, , 1998. They also have the capacity to shelter numerous species, from the juvenile forms to adult phases, which use the environment for feeding, breeding or protection from predators; in addition to resident species, that spend their entire life cycle in estuaries, many of these resources reach high economic and social values (Kennish, 1991(Kennish, , 1998; Barletta and Dantas, 2016).…”

Section: Introductionmentioning

confidence: 99%

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Interannual and Seasonal Variations in Estuarine Water Quality

Costa

Dantas

et al. 2018

Front. Mar. Sci.

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Anthropic processes degrade quality of estuarine environments, resulting in a worrying form of water pollution. The objective of the study was to describe and discuss interannual and seasonal changes of water quality based on indicators monitored in Goiana River estuary, as well as identifying the main drivers of such changes. We considered three estuarine areas or habitats (upper estuary, middle estuary and lower estuary), and two seasons (dry and rainy) for anchoring sample design. The information collected for surface and bottom water include water temperature (• C), salinity, dissolved oxygen (mg L −1), saturation (%) and Secchi depth (cm) (n = 864). The monthly total rainfall (mm) was compiled from public database. Multivariate analyses highlight inter dependency among these parameters. Water quality was reduced in dry periods (including episodes of hypoxia), but generally increased toward the mouth of estuary. Rainfall is the most important factor in the renewal and maintenance waters of small tropical estuaries. Regions most sensitive to climate change where water resources are depleted and/or compromised should pay even more attention to upcoming changes in rainfall (seasonal) and climatic patterns in addition to better water management practices.

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