A preliminary study on multi-level biomarkers response of the tropical oyster Crassostrea brasiliana to exposure to the antifouling biocide DCOIT

Developmental cardiotoxicity of 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one (DCOIT) in marine medaka (Oryzias melastigma)

The application of 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one (DCOIT) as an antifouling biocide causes high toxicity to non-target marine organisms. To examine the developmental cardiotoxicity and mechanisms of DCOIT, we concurrently performed sub-chronic exposure and life-cycle exposure experiments using marine medaka embryos. After sub-chronic exposure to DCOIT at 1, 3, 10, and 33 μg/L, cardiac defects were caused by upregulation of cardiac gene transcriptions, decreasing heart size, and accelerating heartbeat. Hyperthyroidism in medaka larvae was identified as the cause of developmental cardiotoxicity of DCOIT sub-chronic exposure. In addition, parental life-cycle exposure to 1, 3, and 10 μg/L DCOIT led to transgenerational impairment of cardiogenesis in offspring medaka. A crossbreeding strategy discriminated a concentration-dependent mechanism of transgenerational cardiotoxicity. At 1 μg/L, the DCOIT-exposed female parent transferred a significantly higher amount of triiodothyronine (T3) hormone to offspring, corresponding to an accelerated heart rate. However, DCOIT at higher exposure concentrations modified the methylome imprinting in larval offspring, which was associated with cardiac dysfunction. Overall, the findings provide novel insights into the developmental cardiotoxicity of DCOIT. The high risks of DCOIT-even at environmentally realistic concentrations-raise concerns about its applicability as an antifoulant in a marine environment.

Multiple biomarkers in pufferfish as a proxy of environmental health in brazilian marine protected areas

Marine Protected Areas (MPAs) are designed to conserve biodiversity and vulnerable ecosystems. This study aimed to assess the environmental quality of three Brazilian MPAs, based on the integrated analysis of biomarkers in pufferfish. The MPAs are differentiated by the degree of anthropogenic influences. The Barra do Una Estuary sustainable reserve (JUR) is a reference area due to its low levels of contamination and species diversity. The Cananéia Estuarine System (CAN) has been recognized as a biosphere reserve by UNESCO, as well as a Ramsar wetland. This MPA was influenced by upstream mining activities, resulting in the introduction of metals in the estuarine waters and the discharge of untreated urban sewage. The São Vicente estuary (SSV) lacks proper sanitation infrastructure. All collections were conducted during winter season, and, after collection, the animals were euthanized, their soft tissues were removed, and multiple biomarkers were analyzed in the gills and liver, as biometric, genotoxic, biochemical, and morphological. A one-factor multivariate analysis was applied to evaluate the differences between the data sets, and the matrices were analyzed using PERMANOVA to evaluate the "estuary" factor. The results were integrated using PCA with a 0.4 cut value and an Enhanced Integrated Biomarker Response (EIBR) was calculated. PCA was correlated with biochemical, genotoxic, and morphological biomarkers. In general, SVV differed from CAN and JUR as shown by both univariate and multivariate analyses. SVV also showed the highest EIBR, followed by CAN. Organisms from SSV showed greater gill pathology, elevated AChE activity and lipoperoxidation (LPO), and micronuclei frequency. CAN present intermediate EIBR, with severe pathologies in the liver. CAN seems to present an intermediate environmental quality between SSV and JUR indicating the importance of the existence of MPAs for environmental conservation and the need to monitor such areas, to maintain their suitable environmental quality.

Antifouling coatings can reduce algal growth while preserving coral settlement

In the early stages after larval settlement, coral spat can be rapidly overgrown and outcompeted by algae, reducing overall survival for coral reef replenishment and supply for restoration programs. Here we investigated three antifouling (AF) coatings for their ability to inhibit algal fouling on coral settlement plugs, a commonly-used restoration substrate. Plugs were either fully or partially coated with the AF coatings and incubated in mesocosm systems with partial recirculation for 37 days to track fouling succession. In addition, settlement of Acropora tenuis larvae was measured to determine whether AF coatings were a settlement deterrent. Uncoated control plugs became heavily fouled, yielding only 4–8% bare substrate on upper surfaces after 37 days. During this period, an encapsulated dichlorooctylisothiazolinone (DCOIT)-coating was most effective in reducing fouling, yielding 61–63% bare substrate. Antiadhesive and cerium dioxide (CeO_2−x) nanoparticle (NP) coatings were less effective, yielding 11–17% and 2% bare substrate, respectively. Average settlement of A. tenuis larvae on the three types of AF-coated plugs did not statistically differ from settlement on uncoated controls. However, settlement on the NP-coating was generally the highest and was significantly higher than settlement found on the antiadhesive- and DCOIT-coating. Furthermore, on plugs only partially-covered with AF coatings, larval settlement on coated NP- areas was significantly higher than settlement on coated antiadhesive- and DCOIT-areas. These results demonstrate that AF coatings can reduce fouling intensity on biologically-relevant timescales while preserving robust levels of coral settlement. This represents an important step towards reducing fine-scale competition with benthic fouling organisms in coral breeding and propagation.