Concentrations of 11 elements were quantified in five marine species from different trophic levels of a food web (algae, mussel, shrimp and fish), representative for shallow Senegalese coastal waters, and including species of commercial importance. Significant differences in element concentrations and bioaccumulation were demonstrated, revealing the utility of employing a suite of organisms as bioindicators to monitor metal contamination in coastal areas. There was no clear seasonal pattern in concentration of elements, however inter-site differences were observed. Calculations of transfer factors for all the studied elements showed that transfer factors from water were greater than those from sediments. For shrimp and mussel, the concentrations of Pb and Cd were below the EU's maximum level for human consumption, however high concentrations of arsenic in shrimp were recorded at all sites.

International audience | Concentrations of 11 elements were quantified in five marine species from different trophic levels of a food web (algae, mussel, shrimp and fish), representative for shallow Senegalese coastal waters, and including species of commercial importance. Significant differences in element concentrations and bioaccumulation were demonstrated, revealing the utility of employing a suite of organisms as bioindicators to monitor metal contamination in coastal areas. There was no clear seasonal pattern in concentration of elements, however inter-site differences were observed. Calculations of transfer factors for all the studied elements showed that transfer factors from water were greater than those from sediments. For shrimp and mussel, the concentrations of Pb and Cd were below the EU's maximum level for human consumption, however high concentrations of arsenic in shrimp were recorded at all sites.

The revised Bathing Water Directive (rBWD) introduces more stringent standards for microbial water quality and promotes more pro-active management of the beach environment through the production of a bathing water profile (BWP). The aim of this study was to determine whether living seaweeds in the littoral zone are colonised by faecal indicator organisms (FIOs), and to quantify the survival dynamics of waterborne Escherichia coli in microcosms containing senescing seaweeds. Living seaweed (Fucus spiralis) was not associated with FIO colonisation, although could be providing a protected environment in the underlying sand. Senescing seaweeds enhanced waterborne E. coli survival compared to plastic debris, with the brown seaweed Laminaria saccharina facilitating greater E. coli persistence than either Chondrus crispus or Ulva lactuca. This has important implications for FIO survival on bathing beaches as the majority of beach-cast biomass is composed of brown seaweeds, which could support significant levels of FIOs.

The revised Bathing Water Directive (rBWD) introduces more stringent standards for microbial water quality and promotes more pro-active management of the beach environment through the production of a bathing water profile (BWP). The aim of this study was to determine whether living seaweeds in the littoral zone are colonised by faecal indicator organisms (FIOs), and to quantify the survival dynamics of waterborne Escherichia coli in microcosms containing senescing seaweeds. Living seaweed (Fucus spiralis) was not associated with FIO colonisation, although could be providing a protected environment in the underlying sand. Senescing seaweeds enhanced waterborne E. coli survival compared to plastic debris, with the brown seaweed Laminaria saccharina facilitating greater E. coli persistence than either Chondrus crispus or Ulva lactuca. This has important implications for FIO survival on bathing beaches as the majority of beach-cast biomass is composed of brown seaweeds, which could support significant levels of FIOs.

The herbicide irgarol 1051 is commonly used on ship hulls to prevent growth of algae, but as a component of self-eroding paints it can also spread in the surrounding waters and affect non-target organisms. The effect of irgarol on settlement and growth of zoospores from the marine macro algae Ulva lactuca from the Gullmar fjord on the Swedish west coast was investigated in the present study. The zoospores were allowed to settle and grow in the presence of irgarol, but neither settlement – nor growth inhibition was observed at concentrations of up to 2000nmoll−1. This is between 10 and 100 times higher than effect concentrations reported earlier for algae. Irgarol also induced the greening effect (4-fold increase in chlorophyll a content) in the settled zoospore/germling population, typical for photosystem II inhibitors like irgarol. This study support previous findings that irgarol constitutes a selection pressure in the marine environment.

Antifouling biocides are found in the marine ecosystem were they can affect non-target organisms. In this study the effects of five antifouling biocides on the settlement and growth of Ulva lactuca zoospores were investigated. The biocides investigated were copper (Cu²⁺), 4,5-dichloro-2-n-octyl-3(2H)-isothiazolone (DCOIT), triphenylborane pyridine (TPBP), tolylfluanid and medetomidine. Full concentration–response curves where determined for each compound. EC₅₀ values were determined for copper, DCOIT, TPBP and tolylfluanid, all of which inhibited settlement and growth in a concentration dependent manner with the following toxicity ranking; tolylfluanid (EC₅₀ 80 nmol L⁻¹) ~ DCOIT (EC₅₀ 83 nmol L⁻¹) > TPBP (EC₅₀ 400 nmol L⁻¹) > Cu²⁺ (EC₅₀ 2,000 nmol L⁻¹). Medetomidine inhibited settlement and growth only at the extreme concentration of 100,000 nmol L⁻¹ (93 % effect). The low toxicity is possibly a consequence of a lack of receptors that medetomidine can bind to in the U. lactuca zoospores.

From an environmental perspective, there is a need to reduce the amount of biocides from antifouling paints in the marine ecosystem as these biocides can exert a negative effect on the marine life. One way to do this is to optimize the use of biocides in antifouling paints, and thereby avoid unnecessary overdosing. This thesis has been produced within the research program Marine Paint which has the overall aim to produce an antifouling paint with a lower environmental impact than the paints existing on the market today. The aim of the studies presented in this thesis has been to evaluate the efficacy and ecotoxicity of eight antifouling biocides to both target and non-target organisms. The biocides investigated were: medetomidine, triphenylborane pyridine (TPBP), tolylfluanid, copper, irgarol, zinc pyrithione, copper pyrithione and 4,5-dichloro-2-n-octyl 3(2H)-isothiazolone (DCOIT). The target organisms investigated were the macroalga Ulva lactuca and periphyton (i.e. microbial communities). It is important to keep in mind that all target organisms that antifouling biocides are meant to affect, are also non-target organisms when they grow on natural substrates in the marine ecosystem. Therefore, effects on target organisms are not only of interest for efficacy evaluations, but also for ecotoxicological assessments of the biocides. Both the efficacy and ecotoxicity of the eight biocides has been evaluated for the target organisms in settlement assays in which the organisms were allowed to settle and grow in the presence of the biocides. Full concentration-response curves from 0 to 100 % effect were produced to enable future mixture predictions. Such mixture predictions can be used for paint optimization, but also in environmental applications such as hazard assessments. Copper pyrithione was the biocide that most efficiently prevented growth of both Ulva lactuca and periphyton communities, and for Ulva lactuca is was also the biocide with the highest ecotoxicity. Due to different shapes of the concentration-response curves, the toxicity ranking was not consistent at all effect levels (from EC10 to EC98), and irgarol was found to be more toxic to periphyton at lower concentrations than copper pyrithione. In order to extend the ecotoxicological evaluations of the biocides beyond target organisms, effects on the non-target organism Acartia tonsa was investigated. Acartia tonsa is one of the most commonly occurring pelagic calanoid copepods in coastal waters world-wide. Effects on mortality and egg production were studied for three of the eight biocides, namely DCOIT, TPBP and medetomidine. It was shown that neither DCOIT nor medetomidine affected the egg production specifically, but inhibition of egg production occurred at the same concentration as mortality. TPBP was on the other hand shown to affect the egg production at concentrations lower than lethal concentrations. Antifouling biocides present in the marine environment can exert selection pressure on marine life and through the process of natural selection induce tolerance development. An extreme tolerance to the antifouling biocide irgarol in a population of Ulva lactuca from the mouth of the Gullmar fjord has been described. This indicates that the use of antifouling paints has made its imprint on the marine ecosystem. The results from this thesis have deepened the understanding of the biological effects of antifouling biocides. The well-defined concentration-response curves gives information on both efficacy and ecotoxicity, and the information can be used in a number of applications where either biocidal efficacy or ecotoxicity is of interest, such as hazard assessments and in the design of antifouling paints.