Benthic trophic status of aquatic transitional environments with distinct morphological and dynamic characteristics on the south-western Atlantic coast

The benthic trophic status of Uruguayan coastal estuarine habitats (permanently open estuaries and open or closed coastal lagoons) was evaluated, twice in 1 year and at different spatial scales, using the amount and biochemical composition of the sedimentary organic matter. Nested hierarchical ANOVAs were applied to evaluate differences at the habitat level, among sites for each type of estuarine habitat (three estuaries and three lagoons) and between sectors located at different distances from the sea (inner v. outer sectors). Morphological and hydrodynamic differences between the two types of habitats explained site-to-site variations in eutrophic conditions in the open or closed coastal lagoons and meso-oligotrophic conditions in permanently open estuaries. These differences followed the patterns found for sediment grain size, with inner sectors (lower-energy areas) favouring the accumulation of finer sediments and higher amounts of degraded–detrital organic matter. In autumn, biochemical parameters indicated the dominance of aged and more degraded organic matter, with both types of habitats having a low nutritional value no matter which sector was considered. By contrast, in spring, biochemical composition showed the prevalence of fresh and more labile sedimentary organic matter with a high food value, especially in the outer sectors.

Download Full-text

Influence of Seascape on Coastal Lagoon Fisheries: the Role of Habitat Mosaic in the Venice Lagoon

Estuaries and Coasts ◽

10.1007/s12237-021-00986-3 ◽

2021 ◽

Author(s):

Luca Scapin ◽

Matteo Zucchetta ◽

Fabio Pranovi ◽

Piero Franzoi

Keyword(s):

Water Quality ◽

Coastal Lagoons ◽

Spatial Scales ◽

Venice Lagoon ◽

Habitat Characteristics ◽

Artisanal Fishery ◽

Sediment Grain Size ◽

Northern Adriatic ◽

Broad Scale

AbstractFisheries are a staple human activity supported by coastal lagoons. Together with water quality and trophic status, lagoon morphology is acknowledged as one of the main ecological drivers of fishery yields; however, the role of lagoon seascape structure is still poorly understood. This paper investigates how morphological variables, habitat distribution and seascape diversity and complexity affect yields of artisanal fishery performed with fyke nets in the Venice Lagoon (northern Adriatic Sea, Italy). Two spatial scales were considered in the analysis, with water quality parameters (temperature, salinity, dissolved oxygen, turbidity, water residence times, N, P and chlorophyll-a concentrations) being measured at a fine, fyke-net scale and morphological (average bottom elevation and sediment grain size) and habitat features (habitat proportion, diversity and complexity) being measured at a broader, seascape scale. Generalised linear mixed models were employed to model 8 years of nekton and green crab catches, disentangling the role of broad-scale morphology and seascape from that of fine-scale water quality. Broad-scale variables clearly influenced fishery target species. Among them, lagoon residents were associated with specific morphological and habitat characteristics, while marine migrants showed a stronger link with overall habitat diversity and complexity. This evidence emphasises how artisanal fishery in the Venice Lagoon relies on the conservation of morphological and habitat heterogeneity. Moreover, it highlights how habitat restoration performed at the seascape level should also be taken into account, in addition to controlling hydrology and water quality, when managing fishery resources in coastal lagoons.

Download Full-text

Small-scale distribution of metazoan meiofauna and sedimentary organic matter in subtidal sandy sediments (Mediterranean Sea)

Advances in Oceanography and Limnology ◽

10.4081/aiol.2019.8169 ◽

2019 ◽

Vol 10 (1) ◽

Author(s):

Davide Moccia ◽

Alessandro Cau ◽

Maria Carmela Meloni ◽

Antonio Pusceddu

Keyword(s):

Organic Matter ◽

Biochemical Composition ◽

Nutritional Quality ◽

Random Distribution ◽

Sedimentary Organic Matter ◽

Small Scale ◽

Metazoan Meiofauna ◽

Sandy Sediments ◽

Meiofaunal Abundance

While variations in sedimentary organic matter (OM) quantity, biochemical composition and nutritional quality as well as in meiofaunal abundance and assemblage composition at the macro- and mesoscale are relatively well known, information about variations at the microscale is much scarcer. To shed some light on this issue, we tested the null hypothesis by which abundance and composition of the meiofaunal assemblages, and the quantity, biochemical composition and nutritional quality of sedimentary organic matter in coastal shallow environments do not vary within a frame of 1 m2. No significant variation within the frame emerged for OM quantity, nutritional quality, biochemical composition and the abundance of meiofaunal assemblages. On the other hand, the composition of meiofaunal assemblages varied significantly within the frame and exhibited a clear segregation of assemblages farther to the shore, as a likely result of local micro-hydrodynamic conditions. Spatial autocorrelation analysis revealed that lipid and protein sedimentary contents had a random distribution, whereas carbohydrate and biopolymeric C contents and meiofaunal total abundance were characterized by a patchy distribution, with discrete peaks within the sub-frame squares (ca. 0.1 m2). Phytopigments showed a spatial positive autocorrelation distribution, following the micro-hydrodynamic pattern, with patches larger than the sub-frame square, but smaller than the entire one (1 m2). Overall, our results suggest that, within 1 m2 of subtidal sandy sediments, three replicates could be sufficient to assess correctly OM attributes and the abundance of meiofauna, but could be possibly inadequate for assessing meiofaunal assemblages’ composition at a finer scale (<1 m2).

Download Full-text

Mediterranean Coastal Lagoons: The Importance of Monitoring in Sediments the Biochemical Composition of Organic Matter

International Journal of Environmental Research and Public Health ◽

10.3390/ijerph16183466 ◽

2019 ◽

Vol 16 (18) ◽

pp. 3466

Author(s):

Monia Renzi ◽

Francesca Provenza ◽

Sara Pignattelli ◽

Lucrezia Cilenti ◽

Antonietta Specchiulli ◽

...

Keyword(s):

Organic Matter ◽

Biochemical Composition ◽

Coastal Lagoons ◽

Sediment Cores ◽

Management Strategies ◽

Sediment Layer ◽

The European Union ◽

Coastal Zones ◽

Anoxic Conditions ◽

Chl A

Transitional water ecosystems are targeted by the European Union (EU) Water Framework Directive (WFD, CE 2000/60) monitoring programs in coastal zones. Concerning sediments, activities performed for the WFD focus on a few variables concerning the biochemical composition of organic matter. Our research reports the effects of oxygen availability on the biochemical composition of organic matter in sediments to highlight levels of targeted variables in time and, according to the depth of sediment layer, both under oxygenated and anoxic conditions in a mesocosm study on sediment cores. Results provide evidence that tested factors of interest (i.e., disturbance type, oxygenic versus anoxic conditions; persistence time of disturbance, 0–14 days; penetration through sedimentary layers, 0–10 cm depth) are able to significantly affect the biochemical composition of organic matter in sediments. Large part of the variables considered in this study (total organic carbon (TOC), total phosphorous (TP), total sulphur (TS), Fe, carbohydrates (CHO), total proteins (PRT), biopolymeric carbon (BPC), chlorophyll-a (Chl-a) are significantly affected and correlated to the oxygenation levels and could be good early indicators of important changes of environmental conditions. Monitoring activities performed under WFD guidelines and management strategies of Mediterranean coastal lagoon ecosystems shall include the biochemical composition of organic matter in sediment to provide an exhaustive picture of such dynamic ecosystems.

Download Full-text