Nutrient Fluxes from Land to Sea: Consequences of Future Scenarios on the Oder River Basin – Lagoon – Coastal Sea System

Eutrophication management is still one of the major challenges in the Baltic Sea region. Intense transformation processes in several Baltic Sea states have led to drastic changes in e.g., landuse and thereby nutrient emissions and water quality. Several future development directions are possible. The Oder catchment – lagoon – coastal water system serves as a pilot study area, since it has a major influence on the nutrient loads into the Baltic Sea and about 90% of the catchment is located in Poland, a state with transitional economy. Different scenarios for landuse changes in the Oder catchment are developed and their consequences on nutrient emissions simulated. Next to politically induced changes of agricultural landuse in general, specific aspects such as cultivation of energy maize and increased animal stocks are considered. Nitrogen emissions are likely to increase due to agricultural landuse changes whereas phosphorus emissions will not change or even decrease according to the application of the EC‐Urban Waste Water Treatment Directive. Resulting nitrogen loads to the Oder Lagoon could increase up to 23%, phosphorus loads could decrease by 11% compared to 2005. These trends may lead to higher nitrogen availability compared to phosphorus at least in the Oder lagoon. Interannual differences in discharge also have profound effects on nutrient emissions. A good status of the Oder river basin – lagoon – coastal sea system according to EC‐Directives is not very likely to be achieved under the investigated circumstances. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Fish Assemblages in Different Shallow Water Habitats of the Venice Lagoon

The small-sized fish assemblages of the Venice Lagoon were investigated and compared among five shallow subtidal habitats (seagrass beds, sparsely vegetated habitats, unvegetated sand bottoms, mudflats and saltmarsh creeks) in the Northern lagoon basin. Sampling was carried out seasonally (Spring, Summer and Autumn of 2002) in 4–7 stations for each habitat type, by means of a fine-mesh, small beach seine. Two-way analysis of variance was applied to assess the differences in species richness, fish diversity, density and standing stock amongst habitats, whereas fish assemblage composition was investigated by using multivariate analyses (MDS, ANOSIM, SIMPER). The analyses indicated that seagrass beds and saltmarsh creeks are relevant shallow habitats in structuring the small-sized fish assemblages of the Venice Lagoon, supporting specialized and recognizable fish assemblages. Those in seagrass beds, in particular, were characterized by higher species richness and standing stock with respect to all the others. The structuring role of these habitats was discussed in terms of both habitat complexity and degree of confinement. In contrast, sandy bottoms, mudflats and sparsely vegetated habitats were identified as “transition” habitats, with highly variable fish assemblages, influenced by the contribution of the adjacent habitats, and acting probably as both ‘buffer zones’ between the other habitats and migration routes for many fish species in the lagoon.     

Relevance of various formulations of phytoplankton chlorophyll a:carbon ratio in a 3D marine ecosystem model

Numerous experimental studies showed that the phytoplankton Chla-to-Carbon ratio (Chla:C) is highly variable, whereas most of the marine ecosystem models use a constant ratio. In this work, we tested three different formulations for computing the modelled Chla in a 3D coupled hydrodynamical-biogeochemical model of the Southwest lagoon of New Caledonia. The first formulation considers a constant Chla:C ratio. In the second one, Chla is a diagnostic variable related to the variable phytoplankton nitrogen-to-carbon ratio. In the last formulation, Chla is a state variable of the model, which is dynamically simulated. Results showed important differences between the formulations, the first leading to overestimate the Chla concentration in low nutrients conditions. Thus, this study strengthens the importance of the Chla modelling in a coupled model in order to better estimate a crucial variable for validation of ecosystem models.     

Genetic evidence supports a range extension for the Brazilian cownose ray Rhinoptera brasiliensis in the western North Atlantic

We report 24 new records of the Brazilian cownose ray Rhinoptera brasiliensis outside its accepted geographic range. Sequencing of a 442-base pair portion of the mitochondrial NADH dehydrogenase subunit 2 gene for 282 Rhinoptera samples revealed eight records off the east coast of the USA and 16 from the eastern Gulf of Mexico. Both sexes of all life stages were documented in all seasons over multiple years in the Indian River and Lake Worth lagoons, Florida, indicating that their range extends further in the western North Atlantic than previously described.     

Understanding the early ontogenetic stages of Mugil liza (Mugilidae): Morphological traits and digestive/metabolic profile of pre-juveniles after recruitment

The family Mugilidae consists mainly of diadromous species, whose reproduction occurs in offshore waters. Pre-juveniles shift their diet in the surf zone (zooplanktophagous to iliophagous). Later, during their recruitment into estuaries, huge changes take place in their digestive system. However, digestive and metabolic characteristics and some morphological traits at recruitment are unknown for Mugilidae. We performed comparative studies on early and late pre-juveniles of Mugil liza recruited in Mar Chiquita Coastal Lagoon (37°32′–37°45′S, 57°19′–57°26′W, Argentina). We determined digestive enzyme activities (intestine), energy reserves (liver/muscle), total/standard length, total weight, intestinal coefficient, hepatosomatic index and retroperitoneal fat. Pre-juveniles exhibited amylase, maltase, sucrase, lipase, trypsin and aminopeptidase-N (APN) activities, which were maintained over a wide range of pH and temperature, and exhibited Michaelis–Menten kinetics. In late pre-juveniles, amylase (422 ± 131 μmol maltose min⁻¹ mgprot⁻¹), sucrase (86 ± 14 mg glucose min⁻¹ mgprot⁻¹), trypsin (84 ± 9 μmoles min⁻¹ mgprot⁻¹) and APN (0.58 ± 0.08 μmoles min⁻¹ mgprot⁻¹) activities were higher (42%, 28%, 35% and 28%, respectively) than in the early stage. Also, the intestinal coefficient was higher in late (3.04) compared to early (2.06) pre-juveniles. Moreover, the liver appeared to be a main site of glycogen and triglyceride storage in late pre-juveniles, muscle being the site of storage in early pre-juveniles, exhibiting higher glycogen, free glucose and protein concentrations (92%, 82%, 32%, respectively). The results suggest that pre-juveniles of M. liza exhibit an adequate digestive battery to perform complete hydrolysis of various dietary substrates, availability of energy reserves and morphological characteristics to support their feeding habit and growth after recruitment. Our results represent an important contribution to knowledge of the ecology and digestive physiology of pre-juveniles of Mugilidae in the wild.     

Biodiversity and extracellular enzymatic activity of heterotrophic bacterial communities in Bardawil Lagoon,Egypt

The biodiversity of heterotrophic viable bacteria (209 isolates) in the hypersaline Bardawil Lagoon, Egypt, was studied. Composition and extracellular activities of viable culturable heterotrophic bacteria (VCHB) in the water and in non-colonised and seagrass-colonised sediments of Bardawil Lagoon were determined bimonthly during 1997 and 1998. The average ± SD total Kjeldhal nitrogen was 1.69 ± 0.44 mg l^?1 in water, 335.95 ± 19.22 mg kg^?1 in colonised sediments, and 215.5 ± 16.0 mg kg^?1 in non-colonised sediments. Exoenzymatic bacterial activity (glycosidase) presented a seasonal trend with average values of 1.02 ±0.16 μM cm^?3 min^?1 in colonised sediment samples and was 0.36 ± 0.27 μM cm^?3 min^?1 in non-colonised sediments. Mean of VCHB was 4 017 ± 565 cfu g^?1 and 1 195 ± 242 cfu g^?1 for colonised and non-colonised sediments, respectively. Bacterial isolates from Bardawil Lagoon water and sediments yielded a wide diversity of VCHB: a total of 209 different species, belonging to 13 genera from the water and 12 genera from the sediments.     

Biomarkers in Ruditapes decussatus: a potential bioindicator species

The clam Ruditapes decussatus is distributed worldwide and due to its ecological and economical interest has been proposed as a bioindicator in areas where mussels are not available. The accumulation of several anthropogenic compounds in their tissues suggests that they possess mechanisms that allow them to cope with the toxic effects of these contaminants. Besides pollutant uptake, the use of biomarkers is pointed out in this paper since it is a promising approach to monitor the effect of these contaminants in the marine environment. Biomarkers complement the information of the direct chemical characterization of different types of contaminants. Therefore, the aim of this paper is to review the role of several biomarkers: (metallothioneins (MT), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidases (GPx) (total and selenium-dependent), lipid peroxidation (measured as MDA, one of the final products of lipid peroxidation), glutathione S-transferase (GST) and acetylcholinesterase (AChE), measured in different tissues of the clam R. decussatus, in laboratory conditions and under various environmental stresses, in two ecosystems (Ria Formosa lagoon- Portugal) and Bizerta lagoon (Tunisia) in a perspective of a multibiomarker approach to assess environmental changes. Experiment and field studies are in good agreement since MT levels, especially in the gills, the first target tissue of these contaminants, can be used as biomarker of exposure to Cd. GPx and MDA may also be determined in this respect. AChE activity is inhibited by pesticide and, to a less extent, by metal exposure in the gills and whole soft body of clams. However, the induction of GST isoforms experimentally demonstrated is not observed in the field because only global GST activity was determined. The whole set of results opens new research perspectives for the use of this species to assess the effect of mixtures of pollutants in the aquatic environment.     

The presence of exotic Hypnea flexicaulis (Rhodophyta) in the Mediterranean Sea as indicated by morphology, rbcL and cox1 analyses

Here we report the first finding of Hypnea flexicaulis Yamagishi and Masuda in the Mediterranean Sea (Lagoon of Venice, Italy), identified through molecular analyses using the plastid ribulose-1,5-bisphosphate carboxylase/oxygenase (rbcL) and the mitochondrial protein-coding cytochrome c oxidase subunit I (cox1) genes. The phylogenetic reconstruction, based on rbcL + cox1 multiple alignment, showed that all specimens of H. flexicaulis from Venice, Korea, Philippines and Taiwan were included in a monophyletic group supported by a bootstrap value of 100%.It is highly probable that H. flexicaulis has been introduced from Indo-Pacific populations, in particular the Korean one, probably via ship traffic or shellfish transfers.The use of DNA barcoding combined with morphological observations was, in this case, a rapid way to identify this allochthonous species.     

Algal communities of a geothermally heated lagoon on Deception Island (South Shetland Islands)

Kroner Lake, located at Deception Island (Maritime Antarctica), is a unique geothermally heated lagoon in Antarctica. It is declared as special site of scientific interest (SSSI) by Scientific Committee for Antarctic Research (SCAR) for its high biodiversity. A sharp environmental heterogeneity is registered in this lagoon, due to its connection to the sea in its southern margin, and to the input of warm freshwater in the northern one (because of hot springs). This study analyses the biodiversity and abundance of the algal communities (phytoplankton and benthic assemblages) and their relationship with environmental factors. In particular, strong spatial differences of both temperature and conductivity were recorded. The biological studies revealed that the phytoplankton (nanoplankton and microplankton) was dominated by marine diatom species, while the pico-sized fraction was composed by Cyanobacteria Synechococcus-like cells. The epipelon was mainly represented by chain and tubicolous diatoms, among which, Melosira nummuloides was one of the most abundant species. Filamentous Cyanobacteria were also frequently recorded in the algal mats. Kroner Lake is subject to a strong marine influence. Phytoplankton is absolutely dominated by marine diatoms. Spatial variations in temperature and conductivity recorded in the lagoon influence the distribution of the aquatic communities. The greater abundance of pico-sized cells coincided with the warmest site of the water body. Regarding the benthic community, the contribution of freshwater and brackish species is comparatively more important than for the phytoplankton, although the high contribution of marine-derived algae was also evident.