Comparison of multivariate patterns: different taxonomic levels in macrofaunal analysis vs.sediment profiling imagery (SPI)

The multivariate patterns resulting from analyses of macrobenthic abundance data at different taxonomic levels are compared to the pattern derived from various measurements obtained through sediment profiling imagery (SPI). A time-series data set from 1 station in Kiel Bay (Western Baltic) at 22 m depth including macrobenthic and SPI replicates covering 8 yr (1989 to 1996) was analyzed by means of multidimensional scaling (MDS) ordination. The macrobenthos data showed similar patterns, and there was little information loss, with decreasing taxonomic resolution from species to phylum level. The multivariate pattern in the SPI data was not significantly correlated to any of the macrofaunal patterns. However, macrofaunal and SPI patterns seemed to be complementary since they emphasized different aspects of the long-term succession in the Southern Baltic Sea. While macrofaunal patterns were sensitive to anoxia events, changes of SPI-recorded seabed characteristics were primarily related to physical disturbances possibly due to variations in fishing intensity

MERAMOD - predicting the deposition and benthic impact of aquaculture in the Eastern Mediterranean

A model, composed of coupled particle tracking and benthic response modules, for predicting waste solids flux and benthic impacts of gilthead sea bream (Sparus aurata L.) and sea bass (Dicentrarchus labrax L.) aquaculture, was tested at six sites with different hydrodynamics, bathymetries and biomasses in the Aegean and Ionian Seas, Eastern Mediterranean with observations of sediment trap flux and benthic impact indicators. Seven sediment trap validation studies were conducted that varied in design with traps deployed either on the sea bed, attached to nets or in the water column. Model predictions of flux to traps spaced 5 m apart up to 50 m from the cages over a 13 d period were statistically significant (r2 = 0.61, n = 57, p ≤ 0.05). However, the model could not predict adequately the flux to traps spaced 2 m apart in the high-flux zone underneath cages where variability between trap observations was high. In this high-flux zone underneath cages, the averaged model flux predictions resulted in a performance of ± 49%. Statistically significant relationships were established at four sites; between modelled flux and either benthic fauna impact indicator species (S), abundance (A), A/S ratio, Shannon Wiener Index or Biomass Fractionation Index (BFI), (r2 = 0.82, 0.60, 0.57, 0.67 and 0.48, respectively; n = 24, p ≤ 0.05). Two other sites, which did not exhibit an abundance peak in enriched zones, did not fit these relationships. Using relative abundance of taxonomic groups, a modelled flux of 4.1 g m-2 d-1 was a useful boundary; on either side of this boundary, clear trends occurred in pollutant tolerant and intolerant species

Assessing the suitability of a range of benthic indices in the evaluation of environmental impact of fin and shellfish aquaculture located in sites across Europe

The European Union-funded ECASA project (Ecosystem Approach for Sustainable Aquaculture) studied the impacts from aquaculture on ecosystems from northern Norway to Greece. The objectives of this investigation were to identify quantitative indicators of the effects of aquaculture on marine communities, and to assess their applicability over a range of ecosystems and aquaculture production systems. The study included 6 Mediterranean and 4 Atlantic sites, 7 ofwhich produced finfish (seabream, seabass, tuna, salmon and cod), and 2 bivalve molluscs (oysters, mussels, and clams); one site produced both fish and bivalves. Cultivation methods included finfish cages, long-lines and trestles. Similar sampling methodologies were employed at the 10 study sites, obtaining sediment, hydrodynamic, and benthic faunal data. The horizontal impact from organic enrichment extended 50m from the farms, with contradictory responses in several indicators (individual abundance, biomass) and a more consistent response of the Infaunal Trophic Index (ITI) and AZTI'sMarine Biotic Index (AMBI). By means of Partial Redundancy Analysis, it was demonstrated that the environmental variables explained 53.2% of the variability in the macrofaunal variables (individual abundance, species richness, diversity, AMBI and ITI), whilst the explained variance was partialled out within three groups of variables: (i) ‘hydrography’ (depth, distance to farm, average current speed), which explained 11.5% of the variance; (ii) ‘sediment’ (Eh and percentages of silt and total organic matter), which explained 5.4%; and (iii) ‘cages’ (years of production and annual production), which explained 15.2%. The shared variance explained by interactions among these groups was 21.1%. These results, together with multiple regression analysis, provide an accurate assessment of the degree of impact from aquaculture. In conclusion, the use of several benthic indicators, in assessing farm impacts, together with the investigation of dynamics of the studied location, water depth, years of farm activity, and total annual production, must be included when interpreting the response of benthic communities to organic enrichment from aquaculture

Benthic ecology of semi-natural coastal lagoons, in the Ria Formosa (Southern Portugal), Exposed to different water renewal regimes

Several studies in semi-natural coastal lagoons in the Ria Formosa lagoonal system have been carried out. These man-made water reservoirs behave as small lagoons with one opening to the tidal channels, which may be intermittent. Because of their size, these reservoirs are ideal sites for ecological studies. Water quality and macrobenthic fauna were analysed in five water reservoirs. All reservoirs received the same incoming water through a tidal channel, but they differed in water renewal regime. Multidimensional Scaling (MDS) and Discriminant Analysis were used to evaluate the similarity among sites, stations and sampling occasions. Different levels of taxonomic resolution (family, large taxonomic groups and phylum level) were also evaluated. The separation of sites and stations became unclear using high taxonomic levels. Results from the multivariate analyses suggest a slight differentiation of the stations according to sampling occasion but a clear differentiation of the several water reservoirs. Some of the lagoons studied with low water renewal rates showed strong environmental variations. They were characterised by low diversity indexes and abundance of small-sized organisms. Other lagoons, with high water renewal rates, showed low environmental variation and well diversified and structured benthic communities. The main environmental factor that seems to affect the benthic communities was the variation in salinity between neap and spring tides, which is related with the water renewal regime. Coastal lagoons offer a protected shallow habitat, which can be highly productive. Well structured communities, controlled by k-strategists, can develop and settle in leaky lagoons, that is, lagoons with wide entrance channels and tidal currents which guarantee a good water renewal. In these lagoons, biomass can accumulate in large organisms. In contrast, lagoons with a single narrow entrance, that may be closed for long periods, are characterised by persistent physical stress and are dominated by communities of small-sized r-strategists

Exchange of nutrients and oxygen across the sediment-water interface below a Sparus aurata marine fish farm in the north-western Mediterranean Sea

Purpose: This study analyzes the effects of aquaculture activities in open seawater in the north-western coastal waters of the Mediterranean Sea. It is the first of its kind to be based on benthic flux data gathered in situ below fish farms for this particular area. Materials and methods: Samples were collected on four sampling campaigns over a 1-year cycle under a Sparus aurata fish farm facility where benthic fluxes were measured in situ using light and dark benthic chambers. Bottom water and sediment samples were also collected. Data were compared to those for a nearby control station. Results and discussion: Significant differences were found (ANOVA, p < 0. 05) between concentrations of organic matter (OM), total phosphorus and redox potentials in sediments located under the cages and those of the control station. The consumption of dissolved oxygen (DO) by sediment and positive ammonium (NH4 +) fluxes was stimulated by OM content, with correlations of r = -0. 60 (p < 0. 01) and r = 0. 70 (p < 0. 01), respectively. The OM content of sediments was found to be consistently higher under the cages than at the control station, with the highest value (1. 8 ± 0. 7 %) under the cages observed during the early summer; values of DO and NH4 + fluxes were -64 ± 17 and 12. 7 ± 1. 0 mmol m-2 day-1, respectively. PO4 3- fluxes were consistently higher in the fish farm sediments (between 0. 58 and 0. 98 mmol m-2 day-1) than those observed at the control station. Nitrate (NO3 -) fluxes were found to be consistently negative due to denitrification occurring in the sediments and were related to the concentration of NO3 - in bottom waters (r = 0. 92, p < 0. 01). Si fluxes were shown to be associated with water temperature (r = 0. 59, p < 0. 05). Conclusions: The results imply that sediments located below cages accumulate organic matter originating from aquaculture activities, especially during summer months when this activity increases. Sediments undergo biogeochemical changes that mainly affect fluxes of DO, NH4 + and soluble reactive phosphorus, although these do not seem to have a significant impact on the quality of the water column due to the hydrodynamic characteristics of the area. © 2012 Springer-Verlag.We would like to thank the Caja del Mediterraneo for a predoctoral fellowship fund for this research and Antonio Asuncion Acuigroup Maremar manager for the facilities and support in conducting the study. The translation of this paper was funded by the Universidad Politecnica de Valencia, Spain. We are grateful for the valuable comments of the anonymous reviewers on previous versions of the manuscript.Morata Higón, T.; Sospedra, J.; Falco Giaccaglia, SL.; Rodilla Alama, M. (2012). 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Leaf vs. epiphyte nitrogen uptake in a nutrient enriched Mediterranean seagrass (Posidonia oceanica) meadow

In situ nitrogen uptake by leaves and epiphytes was studied in a Mediterranean seagrass (Posidonia oceanica) meadow impacted from a fish farm and a pristine meadow, using 15NH4 and 15NO3 as tracers. In the impacted meadow both leaves and epiphytes yielded higher N concentrations and showed higher specific N uptake, suggesting a linkage between N uptake and its accumulation. Epiphytes took up N faster than leaves in relation to their corresponding biomass, but when assessed per unit area, N uptake was higher in leaves. Leaf N uptake was negatively correlated with epiphyte N uptake. With increasing epiphyte load on leaves, N leaf uptake decreased while N epiphyte uptake increased, indicating that epiphyte overgrowth hinders N uptake by P. oceanica leaves. Epiphyte contribution to total N uptake increased, while that of leaves decreased at the impacted meadow. However, 2\u20133 times less N was transferred daily from the water column to the benthic compartment, through seagrass and epiphyte uptake on total, at the impacted meadow. Therefore, it is probably still the loss of the key species \u2013 the seagrass \u2013 which plays the most important role in N cycling in seagrass ecosystems

Effects of pre-exposure on the tolerance of Artemia salina to oil and oil dispersant

Higher tolerance (acclimation phenomena, adaptation) to oil (Tunisian crude oil) and oil dispersant (Finasol OSR 2, Finasol OSR 5), can be induced in Artemia salina after pre-exposure to these toxicants. The higher tolerance includes acute toxicity (LC50) and sublethal physiological dysfunctions (respiration). High pre-exposure concentrations lead to rapid induction of acclimation phenomena but the higher resistance is partly lost after exposure of the acclimated animals to clean sea water. Exposure to low concentrations of the toxicants induce a slow appearance of adaptation phenomena, but higher tolerance does not disappear after exposure to clean sea water and is strengthened after the detoxification period. © 1986

Effects of pre-exposure on the tolerance of Artemia salina to oil and oil dispersant

Higher tolerance (acclimation phenomena, adaptation) to oil (Tunisian crude oil) and oil dispersant (Finasol OSR 2, Finasol OSR 5), can be induced in Artemia salina after pre-exposure to these toxicants. The higher tolerance includes acute toxicity (LC50) and sublethal physiological dysfunctions (respiration). High pre-exposure concentrations lead to rapid induction of acclimation phenomena but the higher resistance is partly lost after exposure of the acclimated animals to clean sea water. Exposure to low concentrations of the toxicants induce a slow appearance of adaptation phenomena, but higher tolerance does not disappear after exposure to clean sea water and is strengthened after the detoxification period. © 1986