The importance of habitat-type for defining the reference conditions and the ecological quality status based on benthic invertebrates: The Ria Formosa coastal lagoon (Southern Portugal) case study

Abstract

Coastal lagoons are complex systems, with considerable habitat heterogeneity and often subject to high temporal dynamics, which constitutes a great challenge for ecological assessment programs. For defining reference conditions for benthic invertebrates, under the EU Water Framework Directive objectives, historical data from the Ria Formosa leaky lagoon (wet surface area of about 105 km 2 ) located in Southern Portugal was used. The influence of habitat features, such as channel depth, sediment type and seagrass cover, on the expression of these biological communities was inferred by analysing subtidal data collected at stations with different environmental characteristics. Such heterogeneity effect was analysed at the community compositional and structural levels, and also for three indices included in a multimetric Benthic Assessment Tool (BAT). This tool for the assessment of ecological status includes the Margalef index, Shannon-Wiener diversity index, and AZTI's Marine Biotic Index (AMBI). Significant variations associated with environmental features were reflected on specific reference conditions at four habitats in the lagoon. After habitat calibration, the Benthic Assessment Tool (BAT) revealed that, in general and for the period of time covered by this historical data set, the status of the lagoon corresponded to a good ecological condition, which is mainly due to its high water renewal rate. Such classification is in accordance with the majority of studies at the lagoon. However, at punctual sites with human induced high water residence times, significantly lower BAT values were registered. Such community degradation can be associated with physical stress due to salinity increase and to a degradation of water quality, with occurrence of occasional dystrophic crisis, triggered by low water renewal. Habitat 2 differentiation was a crucial step for a correct evaluation of the ecological condition of invertebrate communities across the lagoonal system.

Determining the footprint of sewage discharges in a coastal lagoon in South-Western Europe

“…A microbiological survey considering data from the last 20 years, including some areas close to those of the present work was conducted by Almeida and Soares (2012). Other studies have been carried out in sewage affected areas but are not specifically devoted to water quality issues but rather to ecological issues (Piló et al, 2011;Gamito et al, 2012). Current water quality studies include sites in western Ria Formosa with restricted water exchange such as Ponte Praia de Faro in Ancão Basin and Ramalhete Channel (e.g.…”

“…During the last decades, it has been reported that nitrogen compounds, total organic loads and bivalve microbiological contamination decreased within the Ria Formosa (Brito et al, 2010;Gamito et al, 2012;Cachola and Campos, 2006;Almeida and Soares, 2012). The decline of those compounds and nutrients in particular can be credited to water quality improvement not only by reduced use of agricultural fertilizers (Nitrate Directive compliance; EEC, 1991b) and increased water circulation through Ancão inlet (relocation in 1997;Dias et al, 2009), but also to the STP operational start-up.…”

Impacts of hypoxia on estuarine macroinvertebrate assemblages across a regional nutrient gradient

“…Ulva and Z. marina are both well adapted for shallow, estuarine conditions, and Ulva was sometimes observed at low abundances under oligotrophic conditions within Z. marina-dominated habitat. Unlike Z. marina, which has strict substrate requirements, Ulva grows ephemerally, in nutrient-enriched systems, and is therefore not limited by grain size (Webster et al 1998;Gamito et al 2012). In this study, average substrate particle size (D50) had a greater range at Ulva sites (22-235 μm) compared with Z. marina sites (36-89 μm), presumably due to some combination of higher levels of fine sediment input from agriculture (Alberto et al 2016) and differences in local lithology (van der Poll 1983) and hydrology.…”

The Ecological Sensitivity Evaluation in Yellow River Delta National Natural Reserve

“…1 by data sieving and processing. The data are only from relevant literatures and expert estimation, but also based on field survey and current work as well 33, 38, 42–47.…”