Blanca Figuerola

Assessing the effects of sewage effluents in a Mediterranean creek: fish population features and biotic indices

Sewage effluents are one of the main anthropogenic stressors in Mediterranean rivers. The establishment of a cause–effect relationship is hindered in natural systems by the existence of confounding factors (i.e. biotic interactions). Here we analysed the effects that anthropogenic stressors have on a mono-specific fish community (Iberian redfin barbel population, Barbus haasi) inhabiting the northern edge of its distribution range. In Spring 2004, a total of 40 consecutive sampling sites were surveyed in Vallvidrera creek, and 1,331 specimens were measured and weighed. A principal component analysis was performed to synthesize the information provided by 22 environmental variables. Analysis of variance, bivariate correlation analyses and multiple linear regressions were then used to determine the influence of the environmental gradients built (water quality, hydromorphology, woods and macrophytes, and degree of silting) on fish population features (fish size, body condition status, density and biomass). The findings revealed that water quality was the most significant environmental gradient for this fish population. In particular, fish density decreases and fish length increases in those sites exposed to sewage. Additionally, our results showed the best body condition of those specimens inhabiting fast flow reaches which confirms the rheophilous condition of B. haasi. However, these findings were unnoticed for the current version of the index of biotic integrity using fish as bioindicators in Catalonia. Resource managers need to refine diagnostic tools in order to detect subtle deleterious changes on fish communities before they become evident at population scale. Conservation measures should be focused in these small streams in where the best preserved native fish populations usually inhabit. This study suggests the need to change water management policies in Mediterranean rivers to improve the water quality of sewage effluents and increase the dilution power of these rivers.

Spatial patterns and diversity of bryozoan communities from the Southern Ocean: South Shetland Islands, Bouvet Island and Eastern Weddell Sea

In this study, we report new data on the biodiversity and the geographic and bathymetric distribution of bryozoans collected during the ANT XXI/2 cruise (November 2003 to January 2004) in the Eastern Weddell Sea and Bouvet Island, and during the Spanish Antarctic expedition ECOQUIM (January 2006) in the South Shetland Islands. Our data on distribution were analysed together with previous studies carried out in the same regions. A total of 54 species of Antarctic bryozoans (206 samples), including a new species of the genus Reteporella were found. Two species were reported for the first time from Bouvet Island, one from the Weddell Sea and one from Spiess Seamount. Fifty-five per cent of all species identified were endemic to Antarctica. In the Weddell Sea, the regions of Austasen and Kapp Norvegia exhibit the highest relative species richness, followed by the Vestkapp region. Multivariate and cluster analyses revealed small-scale spatial variability in the community structure along depth and between localities.

Antimicrobial activity of Antarctic bryozoans: an ecological perspective with potential for clinical applications.

The antimicrobial activity of Antarctic bryozoans and the ecological functions of the chemical compounds involved remain largely unknown. To determine the significant ecological and applied antimicrobial effects, 16 ether and 16 butanol extracts obtained from 13 different bryozoan species were tested against six Antarctic (including Psychrobacter luti, Shewanella livingstonensis and 4 new isolated strains) and two bacterial strains from culture collections (Escherichia coli and Bacillus cereus). Results from the bioassays reveal that all ether extracts exhibited antimicrobial activity against some bacteria. Only one butanol extract produced inhibition, indicating that antimicrobial compounds are mainly lipophilic. Ether extracts of the genus Camptoplites inhibited the majority of bacterial strains, thus indicating a broad-spectrum of antimicrobial activity. Moreover, most ether extracts presented activities against bacterial strains from culture collections, suggesting the potential use of these extracts as antimicrobial drugs against pathogenic bacteria.

Feeding repellence in Antarctic bryozoans

The Antarctic sea star Odontaster validus and the amphipod Cheirimedon femoratus are important predators in benthic communities. Some bryozoans are part of the diet of the asteroid and represent both potential host biosubstrata and prey for this omnivorous lysianassid amphipod. In response to such ecological pressure, bryozoans are expected to develop strategies to deter potential predators, ranging from physical to chemical mechanisms. However, the chemical ecology of Antarctic bryozoans has been scarcely studied. In this study we evaluated the presence of defenses against predation in selected species of Antarctic bryozoans. The sympatric omnivorous consumers O. validus and C. femoratus were selected to perform feeding assays with 16 ether extracts (EE) and 16 butanol extracts (BE) obtained from 16 samples that belonged to 13 different bryozoan species. Most species (9) were active (12 EE and 1 BE) in sea star bioassays. Only 1 BE displayed repellence, indicating that repellents against the sea star are mainly lipophilic. Repellence toward C. femoratus was found in all species in different extracts (10 EE and 12 BE), suggesting that defenses against the amphipod might be both lipophilic and hydrophilic. Interspecific and intraspecific variability of bioactivity was occasionally detected, suggesting possible environmental inductive responses, symbiotic associations, and/or genetic variability. Multivariate analysis revealed similarities among species in relation to bioactivities of EE and/or BE. These findings support the hypothesis that, while in some cases alternative chemical or physical mechanisms may also provide protection, repellent compounds play an important role in Antarctic bryozoans as defenses against predators.

Chemical Interactions in Antarctic Marine Benthic Ecosystems

Antarctic marine ecosystems are immersed in an isolated, relatively constant environment where the organisms inhabiting their benthos are mainly sessile suspension feeders. For these reasons, physical and chemical biotic interactions play an essential role in structuring these marine benthic communities (Dayton et al., 1974; Orejas et al., 2000). These interactions may include diverse strategies to avoid predation (e.g. Iken et al., 2002), competition for space or food (e.g. Bowden et al., 2006) and avoiding fouling (e.g. Rittschof, 2001; Peters et al., 2010). For instance, in the marine benthos, one of the most extended effective strategies among sessile soft-bodied organisms is chemical defense, mediated by several bioactive natural products mostly considered secondary metabolites (e.g. Paul et al., 2011). The study of the “chemical network” (chemical ecology interactions) structuring the communities provides information about the ecology and biology of the involved species, the function and the structure of the community and, simultaneously, it may lead to the discovery of new compounds useful to humans for their pharmacological potential (e.g. Avila, 1995; Bhakuni, 1998; Munro et al., 1999; Faulkner, 2000; Lebar et al., 2007; Avila et al., 2008). In the last three decades, the study of marine chemical ecology has experienced great progress, thanks to the new technological advances for collecting and studying marine samples, and the possibility of identification of molecules with smaller amounts of compounds (e.g. Paul et al., 2006, 2011; Blunt et al., 2011).

Chemo–ecological interactions in Antarctic bryozoans

Abstract The role of bioactive metabolites in ecological interactions involving Antarctic bryozoans has been scarcely studied. Bryozoans are one of the most abundant and diverse members of the Antarctic benthos and are preyed upon by diverse kinds of predators. They seem to be casual food items of the common Antarctic sea urchin Sterechinus neumayeri and the ubiquitous omnivorous amphipod Cheirimedon femoratus. In this study, the cytotoxic activity against embryos and sperm of the sea urchin S. neumayeri and the substrate preferences of the amphipod C. femoratus were assessed using organic extracts from Antarctic bryozoans, in order to determine the presence of chemical defenses. New adapted protocols were designed using a solidifying gel for simulating bryozoans’ surface. We analyzed 32 organic extracts from 16 samples that belonged to 13 different bryozoan species. No cytotoxicity was detected against embryos of S. neumayeri, while 12 of the 13 bryozoan species were cytotoxic to sperm at natural concentrations. In the substrate preference assays, the amphipod C. femoratus was repelled by ten species. The variable bioactivities found in both types of organic partitions of extracts indicated the presence of both lipophilic and hydrophilic defenses. Inter- and intraspecific variability of chemical defenses was detected also, suggesting environmental-induced responses, symbiotic production, and/or genetic variability. Possible alternative defensive mechanisms are also discussed for species with low or no chemical defense. Our results clearly support the fact that chemically mediated bioactivity in Antarctic bryozoans is common, and there is a likely ecological role of cytotoxic and repellent compounds for their protection.

Cytotoxic Activity of Antarctic Benthic Organisms Against the Common Sea Urchin Sterechinus neumayeri

Antarctic benthic communities below anchor ice and ice scour are subjected to intense biotic interactions, and this has propitiated the development of chemicals to avoid predation, competition, and/or fouling avoidance. In particular, Sterechinus neumayeri, a common eurybathic sympatric sea urchin species, can have a negative effect on early recruitment of benthic organisms through grazing. An adaptive response of these co-existing benthic animals may consist in displaying cytotoxic activities, poorly investigated so far in Antarctic ecosystems, in order to prevent the settlement of embryos and larvae of this sea urchin on them or near and, consequently, to decrease its grazing pressure. Cytotoxic activities of Antarctic benthic organisms, mainly from the deep waters of the poorly surveyed area of the eastern Weddell Sea, were assessed against embryos and sperm of the sea urchin S. neumayeri. A new methodology based in a standardized protocol was adopted for this species. Bioassays were performed at Deception Island (South Shetland Islands) during the Austral Summers of 2008-2009 and 2009-2010, using ether extracts at different concentrations from different benthic organisms collected in previous Antarctic expeditions. A high percentage (80%) of the species tested (29) from eight different phyla (Porifera, Echinodermata, Cnidaria, Chordata, Bryozoa, Annelida, Nemertea and Hemichordata) were toxic in one or both experiments. In the bioassay of cytotoxicity against embryos, seven of the 14 species (50%) tested did not reach the blastula stage at the highest extract concentration. In the case of the cytotoxicity against sperm, a total of 20 species were tested and all the extracts except one were toxic to the sperm at the maximum concentration. In addition, 6 species were dissected into parts to investigate the possible allocation of defensive compounds. Our results highlight the important role of cytotoxic activity of some Antarctic benthic organisms as a possible chemical defense and/or mechanism of competition for space or food against this common sea urchin.