Design and implementation of two surveys targeted at describing fouling communities and identifying non-native species within active ports

Ports have long been considered ‘high-risk’ areas for the introduction of non-native species (NNS) and should therefore be a focus of NNS monitoring. The industrial nature of active ports can, however, provide various problems when attempting to carry out monitoring programmes. Current methodologies designed to identify NNS and to describe fouling communities have not been developed specifically for use in active ports and can encounter a number of issues when used in these environments. Here, two surveys were developed and trialled within an active port in South Wales, UK, designed to describe fouling communities, identify NNS and overcome some of the major limitations to conducting surveys within ports. Over a 6-month period, fouling communities dominated by solitary ascidians developed in each survey. Seven NNS were identified, mostly species already recorded in the 1950s, including the Mediterranean crab Brachynotus sexdentatus, and the more recently introduced Japanese skeleton shrimp Caprella mutica. Each survey was evaluated independently with respect to key factors, including the ability to detect NNS and practical aspects of using these survey methods in an applied context. We conclude that whilst each survey can function independently, the use of both survey types in conjunction offers the most robust solution to identifying NNS and describing wider fouling communities within active ports. This research has implications for the future monitoring and management of NNS within UK ports.

Caprellid amphipods (Caprella spp.) are vulnerable to both physiological and habitat-mediated effects of ocean acidification

Ocean acidification (OA) is one of the most significant threats to marine life, and is predicted to drive important changes in marine communities. Although OA impacts will be the sum of direct effects mediated by alterations of physiological rates and indirect effects mediated by shifts in species interactions and biogenic habitat provision, direct and indirect effects are rarely considered together for any given species. Here, we assess the potential direct and indirect effects of OA on a ubiquitous group of crustaceans: caprellid amphipods (Caprella laeviuscula and Caprella mutica). Direct physiological effects were assessed by measuring caprellid heart rate in response to acidification in the laboratory. Indirect effects were explored by quantifying caprellid habitat dependence on the hydroid Obelia dichotoma, which has been shown to be less abundant under experimental acidification. We found that OA resulted in elevated caprellid heart rates, suggestive of increased metabolic demand. We also found a strong, positive association between caprellid population size and the availability of OA-vulnerable O. dichotoma, suggesting that future losses of biogenic habitat may be an important indirect effect of OA on caprellids. For species such as caprellid amphipods, which have strong associations with biogenic habitat, a consideration of only direct or indirect effects could potentially misestimate the full impact of ocean acidification.

Seasonal population dynamics of the non-native Caprella mutica (Crustacea, Amphipoda) on the west coast of Scotland

Information on the life history and population dynamics of non-native species is essential to understand the process of invasion and impacts on invaded ecosystems. The non-native marine caprellid amphipod Caprella mutica has successfully established populations on coastlines throughout the temperate northern hemisphere and in New Zealand in the southern hemisphere. The introduction mechanism has been surpassed and it is now important to understand its ecology and biology in non-native habitats. The seasonal population dynamics of C. mutica were investigated over 18 months at four sites with different levels of anthropogenic disturbance on the west coast of Scotland. Abundance of C. mutica fluctuated seasonally at all sites, peaking during June to October. The highest abundance recorded on a single mesh collector was 319 000 individuals m−2 in August 2004 at one of the fish farms. Both seasonal and site-specific factors influenced the population dynamics of C. mutica. Both males and females were significantly larger and more abundant at the fish farm sites. Individuals displayed reproductive characteristics at a smaller size at the fish farm sites, indicating earlier maturity. The results suggest that anthropogenic disturbance and artificial resource enhancement contribute to the global establishment success of non-native C. mutica.