Ana B. Bugnot

Eco‐engineering urban infrastructure for marine and coastal biodiversity: Which interventions have the greatest ecological benefit?

1.Along urbanised coastlines, urban infrastructure is increasingly becoming the dominant habitat. These structures are often poor surrogates for natural habitats, and a diversity of eco-engineering approaches have been trialled to enhance their biodiversity, with varying success. 2.We undertook a quantitative meta-analysis and qualitative review of 109 studies to compare the efficacy of common eco-engineering approaches (e.g. increasing texture, crevices, pits, holes, elevations and habitat-forming taxa) in enhancing the biodiversity of key functional groups of organisms, across a variety of habitat settings and spatial scales. 3.All interventions, with one exception, increased the abundance or number of species of one or more of the functional groups considered. Nevertheless, the magnitude of effect varied markedly among groups and habitat settings. In the intertidal, interventions that provided moisture and shade had the greatest effect on the richness of sessile and mobile organisms, while water-retaining features had the greatest effect on the richness of fish. In contrast, in the subtidal, small-scale depressions which provide refuge to new recruits from predators and other environmental stressors such as waves, had higher abundances of sessile organisms while elevated structures had higher numbers and abundances of fish. The taxa that responded most positively to eco-engineering in the intertidal were those whose body size most closely matched the dimensions of the resulting intervention. 4.Synthesis and applications: The efficacy of eco-engineering interventions varies among habitat settings and functional groups. This indicates the importance of developing site-specific approaches that match the target taxa and dominant stressors. Furthermore, because different types of intervention are effective at enhancing different groups of organisms, ideally a range of approaches should be applied simultaneously to maximise niche diversity. This article is protected by copyright. All rights reserved.

Structural alterations in the male reproductive system of the freshwater crayfish, Cherax quadricarinatus (Decapoda, Parastacidae).

No diseases affecting reproductive performance have been previously reported in freshwater crayfishes. This study aims to characterise one reproductive system abnormality found in males of Cherax quadricarinatus reared in captivity. Fifteen adult males of C. quadricarinatus (70-110 g) were purchased from San Mateo S.A. farm (Entre Ríos, Argentina) each season during 2007. Macroscopic analysis showed that 26.6% of the animals sacrificed in winter presented brownish distal vasa deferentia. Histological analysis showed different levels of structural abnormality in the epithelium of the vasa deferentia and spermatophore. Granular and hyaline haemocytes were identified within the vasa deferentia but no significant differences were found in the sperm count between normal and brownish vas deferens. Histological analysis of the crayfishes sacrificed in autumn also showed these modifications in 22% of the animals, however, they did not show the brownish colour under macroscopic analysis. The similarities between the male reproductive system syndrome in shrimps and the abnormalities found in C. quadricarinatus are notable. An unspecific response to thermic stress is a possible explanation of these structural alterations.

Patterns of the Non-Indigenous Isopod Cirolana harfordi in Sydney Harbour

Biological introductions can alter the ecology of local assemblages and are an important driver of global environmental change. The first step towards understanding the impact of a non-indigenous species is to study its distribution and associations in the invaded area. In Sydney Harbour, the non-indigenous isopod Cirolana harfordi has been reported in densities up to 0.5 individuals per cm2 in mussel-beds. Abundances of this species have, however, been largely overlooked in other key habitats. The first aim of this study was to evaluate the abundances and distribution of C. harfordi across different habitats representative of Sydney Harbour. Results showed that C. harfordi occurred in oyster and mussel-beds, being particularly abundant in oyster-beds. We also aimed to determine the role of C. harfordi as a predator, scavenger and detritus feeder by investigating the relationships between densities of C. harfordi and (i) the structure of the resident assemblages, and (ii) deposited organic matter in oyster-beds. Densities of C. harfordi were not related to the structure of the assemblages, nor amounts of deposited organic matter. These findings suggested little or no ecological impacts of C. harfordi in oyster-beds. These relationships may, however, affect other variables such as growth of individuals, or be disguised by high variability of assemblages among different locations. Future studies should, therefore, test the impacts of C. harfordi on the size of organisms in the assemblage and use manipulative experiments to control for spatial variation. This study is the first published work on the ecology of the invasion of C. harfordi and provides the starting-point for the study of the impacts of this species in Sydney Harbour.

Artificial structures alter kelp functioning across an urbanised estuary

Assessments of human impacts on natural habitats often focus on the abundance of component species, yet physiological and/or sub-lethal effects of stressors on functional attributes may be equally important to consider. Here we evaluated how artificial structures, an integral part of urbanisation in the marine environment, affects key functional properties of the habitat-forming kelp Ecklonia radiata. Given that stressors rarely occur in isolation, we assessed the effects of infrastructure across an urbanised estuary. Estuaries are ideal for studying how multiple anthropogenic and natural stressors influence potential impacts of infrastructure on habitat-forming species because these habitats usually face a wide range and levels of stressors. Here, we compared the abundance of habitat-forming macro-algae as well as the growth, erosion and photosynthetic activity of kelp in artificial and natural habitats across one of the largest urbanised estuaries in the word - Sydney Harbour. We predicted that effects of artificial structures on functional attributes of kelps would be stronger in the inner area of the Harbour, characterised by higher levels of human impacts and low flushing. Contrary to our predictions, we found that effects of infrastructure were consistent across the estuary, regardless of the ecological footprint caused by human activities or natural environmental gradients. When differences were observed between areas of the estuary, they mostly occurred independently of impacts of substrate type. Importantly, we found lower erosion rates of kelp on pilings than on reefs, likely resulting in lower production of detritus in estuaries where natural reefs are degraded or lost and pilings added. Such impacts have important implications for the connectivity among coastal habitats and secondary productivity in adjacent and remote habitats, which are highly dependent on the exportation of kelp detritus. Our study is the first to assess potential functional consequences of urbanisation through physiological and/or biomechanical effects on habitat-formers, an often overlooked mechanism of environmental impact on ecosystem functioning.

A novel framework for the use of remote sensing for monitoring catchments at continental scales

Historical ecology can teach us valuable lessons on the processes and drivers of environmental change that can inform future monitoring priorities and management strategies. Environmental data to study environmental history, however, is often absent or of low quality. Even when studying changes occurring during the last few decades, monitoring efforts are scarce due to logistical and cost limitations, leaving large areas unassessed. The aim of this study is to evaluate the use of estuarine water colour as an indicator of historical environmental change in catchments. Water colour change was assessed in estuaries in Australia from 1987 to 2015 using satellite remote sensing. Random points were selected for each estuary and applied to the Australian Geoscience Data Cube (based on Landsat images) to obtain reflectance data through time. We propose a framework where (i) water colour is used to detect historical changes in catchments using generalised additive models, (ii) possible stressors and pressures driving those changes are evaluated using other available historical data, and (iii) lessons learned inform appropriate monitoring and management actions. This framework represents a novel approach to generate historical data for large-scale assessments of environmental change at catchment level, even in poorly studied areas.