A deep dive into the ecology of Gamay (Botany Bay, Australia): current knowledge and future priorities for this highly modified coastal waterway

Context: Gamay is a coastal waterway of immense social, cultural and ecological value. Since European settlement, it has become a hub for industrialisation and human modification. There is growing desire for ecosystem-level management of urban waterways, but such efforts are often challenged by a lack of integrated knowledge. Aim and methods: We systematically reviewed published literature and traditional ecological knowledge (TEK), and consulted scientists to produce a review of Gamay that synthesises published knowledge of Gamay’s aquatic ecosystem to identify knowledge gaps and future research opportunities. Key results: We found 577 published resources on Gamay, of which over 70% focused on ecology. Intertidal rocky shores were the most studied habitat, focusing on invertebrate communities. Few studies considered multiple habitats or taxa. Studies investigating cumulative human impacts, long-term trends and habitat connectivity are lacking, and the broader ecological role of artificial substrate as habitat in Gamay is poorly understood. TEK of Gamay remains a significant knowledge gap. Habitat restoration has shown promising results and could provide opportunities to improve affected habitats in the future. Conclusion and implications: This review highlights the extensive amount of knowledge that exists for Gamay, but also identifies key gaps that need to be filled for effective management

Nonindigenous biota on artificial structures: could habitat creation facilitate biological invasions?

We identified different distributions of marine nonindigenous species (NIS) and native species on some artificial structures versus natural reefs and using experimental manipulations, revealed some possible causal mechanisms. In well-established subtidal assemblages, numbers of NIS were 1.5–2.5 times greater on pontoons or pilings than on rocky reefs, despite the local species pool of natives being up to 2.5 times greater than that of NIS. Conversely, on reefs and seawalls, numbers of native species were up to three times greater than numbers of NIS. Differential recruitment to different positions and types of surfaces appeared to influence distribution patterns. NIS recruited well to most surfaces, particularly concrete surfaces near the surface of the water, whilst natives occurred infrequently on wooden surfaces. The position of rocky reefs and seawalls close to the shore and to the seabed appeared to make them favourable for the recruitment of natives, but this positioning alone does not hinder the recruitment of NIS. We argue that pontoons and pilings represent beachheads (i.e. entry points for invasion) for many nonindigenous epibiota and so enhance the spread and establishment of NIS in estuaries. Habitat creation in estuaries may, therefore, be a serious threat to native biodiversity

Fish assemblages in habitats dominated by Caulerpa taxifolia and native seagrasses in south-eastern Australia

Seagrass beds in estuaries are important habitats and nursery grounds for a great variety of fishes, including many economically important species. The introduction of the invasive green alga Caulerpa taxifolia could potentially threaten the seagrasses of south-eastern Australia. This study examined the implications of the spread of C. taxifolia on ichthyofauna in 2 estuaries in central New South Wales. Fish assemblages were compared among adjacent habitats of C. taxifolia and 2 seagrass species (Posidonia australis and Zostera capricorni). Fish were sampled using a small beam trawl to test for differences among habitats in (1) the species composition of the fish assemblages, (2) total abundance and species richness of fishes, and (3) abundances of major fish families. Fish assemblages separated into 3 significantly distinct groupings based on habitat. Total abundances of fishes were similar among habitats; however, species richness was lower in C. taxifolia. The fish assemblages in C. taxifolia were largely characterised by high abundances of gobiid fishes, similar to those in Z. capricorni, and few or no syngnathid and monacanthid species when compared to seagrass fish assemblages. This suggests that if C. taxifolia competitively replaces native seagrass beds in the estuaries of New South Wales, the resulting change in habitat may also cause a change in fish assemblages. This could reduce the abundances of some protected and economically important fish species but may also increase abundances of other opportunistic fishes. © Inter-Research 2006

Nonindigenous biota on artificial structures: could habitat creation facilitate biological invasions?

We identified different distributions of marine nonindigenous species (NIS) and native species on some artificial structures versus natural reefs and using experimental manipulations, revealed some possible causal mechanisms. In well-established subtidal assemblages, numbers of NIS were 1.5–2.5 times greater on pontoons or pilings than on rocky reefs, despite the local species pool of natives being up to 2.5 times greater than that of NIS. Conversely, on reefs and seawalls, numbers of native species were up to three times greater than numbers of NIS. Differential recruitment to different positions and types of surfaces appeared to influence distribution patterns. NIS recruited well to most surfaces, particularly concrete surfaces near the surface of the water, whilst natives occurred infrequently on wooden surfaces. The position of rocky reefs and seawalls close to the shore and to the seabed appeared to make them favourable for the recruitment of natives, but this positioning alone does not hinder the recruitment of NIS. We argue that pontoons and pilings represent beachheads (i.e. entry points for invasion) for many nonindigenous epibiota and so enhance the spread and establishment of NIS in estuaries. Habitat creation in estuaries may, therefore, be a serious threat to native biodiversity

Enhanced numbers of two temperate reef fishes in a small, partial-take marine protected area related to spearfisher exclusion

Reviews of global studies suggest that even small no-take marine protected areas (MPAs) can have localized benefits on harvested organisms of varying mobility. The generality of this conclusion, however, has been questioned due to poor experimental designs of some studies included in reviews, and the relatively small proportion of studies which focused on very small MPAs (≤1 km²). Here we use a correlative approach to test for possible effects of a 0.1 km² partial-take MPA (closed to spearfishing for 12.5 years) on the abundance and size of key harvested fishes using an asymmetrical spatial comparison of the MPA vs. three unprotected control areas. Positive impacts were detected, despite our prediction that a small MPA would not provide protection to highly mobile taxa. Densities of legal-sized (≥200 mm SL) Cheilodactylus fuscus (red morwong; relatively sedentary) were 2.8 times greater within the MPA than at the controls and densities of legal-sized Acanthopagrus australis (yellow-fin bream; relatively mobile) were 2.3 times greater on shallow (≤3.5 m) but not deeper (4–12 m) areas of reef within the MPA. While benefits of protection were evident, the cost-benefit of implementing similar MPAs should be carefully considered as the partial protection status and small size of the MPA limit both the adequacy of the MPA for protecting a larger range of species, and the magnitude and thus detectability of effects

Clarification on the applicability of systematic reviews Reply

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Comparing salinity tolerance in early stages of the sporophytes of a non-indigenous kelp (Undaria pinnatifida) and a native kelp (Saccharina latissima)

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