Amy Louise Swift

Abstract

 The marine environment is facing several threats, many of which are caused or exacerbated by anthropogenic pressures. Amongst the four most detrimental is the impact of non-native species on their introduced environment, alongside habitat loss and overexploitation of resources. Such introductions outside of a species natural

range can lead to irreversible changes in benthic community structure and in the long-term, can result in local extinctions. The transportation of non-native species has been an issue ever since humans first started travelling across the sea. Over the centuries, the pressures have grown due to the increase in the number of sea going vessels, the reduction in journey times and the raised vulnerability of the marine environment. The main human-mediated vectors are ballast water and the hulls of vessels. Commercial ships were previously considered the priority for monitoring and regulations, though it has since been established that recreational vessels have a major part to play in the introductions and secondary spread of non-indigenous species (NIS). In part due to the lack of regulations in place, allowing them to set sail

with heavily fouled hulls to distant locations. Not all dispersed species can become invasive and colonising their new environment, although all species should be considered as a potential threat, for if left unmonitored, can become problematic. Local, national, and international bodies have been working on the implementation of guidelines and policies to aid in the mitigation of impacts caused by the pressures of NIS, specifically focusing on recreational vessels and marinas. In turn, working to achieve or re-establish the Marine Strategy Framework Directive (MSFD) Descriptor (2), requiring that human-mediated activities do not influence alterations of the marine ecosystem through the introduction of NIS.

Gibraltar has not been spared of this, failing to achieve its aim due, in part to the establishment of the invasive algae Rugulopteryx okamurae. The most recent consultation report states that monitoring programmes are now in place with the aim of reaching targets to achieve the reduction in spread and abundance of NIS using benthic and intertidal surveys and citizen science data. Local and regional efforts in the obtention of GES for this descriptor are hindered by the lack of biosecurity management of marinas despite the understanding that they are hotspots for introduction and spread of NIS. As a first in Gibraltar, this comprehensive study aimed to assess the presence of NIS in the territorial waters. Focusing on marinas as hotspots, in particular, the Mid Harbour Small Boats Marina (MHSBM). Developing a rapid assessment survey protocol which can be used in other marinas in Gibraltar and further afield, using accessible methods. Using visual methods to acquire and annotate footage from floating pontoons and removing scrape samples for species identification. Using a semi-quantitative ranking system, the level of fouling present on the vessels at the marina was evaluated. In addition, a questionnaire was distributed to the boat owners, to gain an understanding of the behaviour and knowledge of NIS to inform marine management on the inclusion of educational

outreach programs to facilitate monitoring and reduce environmental impacts.

The discovery of NIS species in the present study, including the invasive amphipod Caprella scaura and the colonial bryozoan Amathia verticillata, emphasises the necessity of implementing regular rapid assessment surveys to evaluate the changes in presence and abundance of such species in MHSBM and the other marinas in the territory. The level of fouling on the vessels highlighted the presence of biofilm and macrofouling, including some vessels with near total coverage of the hull and niche areas. Findings from the questionnaire are of particular use in future stakeholder engagement, highlighting the lack of awareness of recreational vessels as vectors of introduction and secondary spread. The inclusion of visual footage of floating pontoons can be used as a training and first identification tool in monitoring the build-up of fouling and the detection of at-risk areas in the marina and in vulnerable habitats within the territorial waters. Implementation of future rapid assessments will aid in the detection of new arrivals, in reaching the MSFD targets and most importantly, in protecting the rich biodiversity of this unique hotspot, at the meeting point of the Atlantic Ocean and the Mediterranean Sea. A vital ecosystem for marine life, providing goods and services to society.

Read more about Amy’s research here.

Keywords: Recreational boating – Marinas – Non-indigenous species – Hull fouling

Primary Supervisor:                  Dr Awantha Dissanayake

Secondary Supervisor:             Dr Jaime Davis

In conjunction with:

Ken Ruiz                                  Mid Harbour Small Boat Marina Committee

Lilli Marie Blume

 Abstract

 Over the last decades the number of marine invasive species around the world has increased as a consequence of high anthropogenic mobility, i.e., in particular shipping traffic, the destruction and degradation of habitat resilience, caused by e.g., exploitation or pollution, and the progressing change to a globally warmer climate. The arrival of invasive species to a recipient ecosystem can have drastic effects on the local communities. One of the more recent invaders in the Mediterranean and the Strait of Gibraltar is the brown seaweed Rugulopteryx okamurae. Algae provide and form habitat for many species of epifaunal invertebrates, a change in algal species composition and resulting changes in the habitat structural complexity can influence these communities. To test the effect that R. okamurae and especially its structural complexity has on the native invertebrate fauna of Gibraltar, algae was collected from four locations during summer. The interstitial space index was calculated as an approximate representation of the algal complexity and the epifauna was counted and identified. The study aimed to test two hypothesis: Firstly, the complexity of R. okamurae is different at the chosen locations corresponding to different levels of relative exposure to drag and secondly, the epifaunal assemblages will differ from each other. A total of 11 taxonomic groups were identified. Most abundant groups were amphipods, followed by isopods, and gastropods. The study found several significant differences for both, algal complexity and epifaunal diversity using both univariate and multivariate analysis. However, no universal patterns were found for differences between locations, neither for the algal complexity nor the epifaunal diversity. The diversity and complexity differed between the two sheltered locations. Highest complexity coincided with highest diversity and vice versa, lowest complexity of R. okamurae coincided with lowest diversity in the epifaunal assemblage. The results suggest that relative exposure to drag force influences the morphology of Rugulopteryx okamurae, displaying a finely fronded morphotype that is reduced in height, in locations less exposed to water flow. Further, data indicates that morphological complexity of R. okamurae and the epifaunal diversity are positively correlated, where higher complexity promotes diversity. This study gives a first insight into the ecological role R. okamurae assumes in the coastal communities of Gibraltarian waters and highlights, the need for research on the connection between environmental factors and algal complexity, and further the resulting impacts on the associated communities.

Read more about Lilli’s research here.

Keywords: Habitat complexity, Epifauna, Rugulopteryx okamurae, Gibraltar

Primary supervisor:                  Dr Awantha Dissanayake

Secondary supervisor:             Dr Darren Fa