Fish use of restored mangroves matches that in natural mangroves regardless of forest age
The loss and degradation of mangrove forests have triggered global restoration efforts to support biodiversity and ecosystem services, including fish stock enhancement. As mangrove restoration accelerates, it is important to evaluate outcomes for species that play functional roles in ecosystems and support services, yet this remains a clear knowledge gap. There is remarkably little information, for example, about how fish use of mangroves varies as restored vegetation matures, hampering efforts to include fisheries benefits in natural capital assessments of restoration. We used unbaited underwater cameras within two distinct zones of mangrove forests—fringe and interior—at five pairs of restored-natural mangrove sites of increasing age from restoration in southeast Queensland, Australia. We used deep learning to automatically extract data for the four most common species: yellowfin bream (Acanthopagrus australis), sea mullet (Mugil cephalus), common toadfish (Tetractenos hamiltoni), and common silverbiddy (Gerres subfasciatus). The abundance of these species varied among sites and zones, but was equal or greater in restored sites compared to paired natural sites. Despite younger restored sites having dramatically lower structural vegetation complexity, abundances did not increase with restoration site maturity. Furthermore, while yellowfin bream and sea mullet were more abundant in the fringe zone, we observed similarities in how fish used fringe and interior zones across all sites. Our paired, space-for-time design provides a powerful test of restoration outcomes for fish, highlighting that even newly restored sites with immature vegetation are readily utilized by key fish species.
Kitchingman ME, Sievers M, Lopez-Marcano S, Connolly RM (2022). Fish use of restored mangroves matches that in natural mangroves regardless of forest age. Restoration Ecology e13806.
As efforts to restore coastal habitats accelerate, it is critical that investments are targeted to most effectively mitigate and reverse habitat loss and its impacts on biodiversity. One likely but largely overlooked impediment to effective restoration of habitat-forming organisms is failing to explicitly consider non-habitat-forming animals in restoration planning, implementation, and monitoring. These animals can greatly enhance or degrade ecosystem function, persistence, and resilience. Bivalves, for instance, can reduce sulfide stress in seagrass habitats and increase drought tolerance of saltmarsh vegetation, whereas megaherbivores can detrimentally overgraze seagrass or improve seagrass seed germination, depending on the context. Therefore, understanding when, why, and how to directly manipulate or support animals can enhance coastal restoration outcomes. In support of this expanded restoration approach, we provide a conceptual framework, incorporating lessons from structured decision-making, and describe potential actions that could lead to better restoration outcomes using case studies to illustrate practical approaches.
Sievers M, Brown CJ, Buelow CA, Hale R, Ostrowski A, Saunders MI, Silliman BR, Swearer SE, Turschwell MP, Valdez SR, Connolly RM (20220. Greater consideration of animals will enhance coastal restoration outcomes. BioScience
Ecosystems remain under enormous pressure from multiple anthropogenic stressors. Manipulative experiments evaluating stressor interactions and impacts mostly apply stressors under static conditions without considering how variable stressor intensity (i.e. fluctuations) and synchronicity (i.e. timing of fluctuations) affect biological responses. We ask how variable stressor intensity and synchronicity, and interaction type, can influence how multiple stressors affect seagrass. At the highest intensities, fluctuating stressors applied asynchronously reduced seagrass biomass 36% more than for static stressors, yet no such difference occurred for photosynthetic capacity. Testing three separate hypotheses to predict underlying drivers of differences in biological responses highlighted alternative modes of action dependent on how stressors fluctuated over time. Given that environmental conditions are constantly changing, assessing static stressors may lead to inaccurate predictions of cumulative effects. Translating multiple stressor experiments to the real world, therefore, requires considering variability in stressor intensity and the synchronicity of fluctuations.
Ostrowski A, Connolly RM, Brown CJ, Sievers M (2022). Fluctuating fortunes: Stressor synchronicity and fluctuating intensity influence biological impacts. Ecology Letters
Predicting the impacts of multiple stressors is important for informing ecosystem management but is impeded by a lack of a general framework for predicting whether stressors interact synergistically, additively or antagonistically. Here, we use process-based models to study how interactions generalise across three levels of biological organisation (physiological, population and consumer-resource) for a two-stressor experiment on a seagrass model system. We found that the same underlying processes could result in synergistic, additive or antagonistic interactions, with interaction type depending on initial conditions, experiment duration, stressor dynamics and consumer presence. Our results help explain why meta-analyses of multiple stressor experimental results have struggled to identify predictors of consistently non-additive interactions in the natural environment. Experiments run over extended temporal scales, with treatments across gradients of stressor magnitude, are needed to identify the processes that underpin how stressors interact and provide useful predictions to management.
Turschwell MP, Connolly SR, Schäfer RB, De Laender F, Campbell MD, Mantyka-Pringle C, Jackson MC, Kattwinkel M, Sievers M, Ashauer R, Côté IM, Connolly RM, van den Brink PJ, Brown CJ (2022). Interactive effects of multiple stressors vary with consumer interactions, stressor dynamics and magnitude. Ecology Letters 25, 1483-1496.
There is an urgent need to halt and reverse loss of mangroves and seagrass to protect and increase the ecosystem services they provide to coastal communities, such as enhancing coastal resilience and contributing to climate stability. Ambitious targets for their recovery can inspire public and private investment in conservation, but the expected outcomes of different protection and restoration strategies are unclear. We estimated potential recovery of mangroves and seagrass through gains in ecosystem extent to the year 2070 under a range of protection and restoration strategies implemented until the year 2050. Under a protection-only scenario, the current trajectories of net mangrove loss slowed, and a minor net gain in global seagrass extent (∼1%) was estimated. Protection alone is therefore unlikely to drive sufficient recovery. However, if action is taken to both protect and restore, net gains of up to 5% and 35% of mangroves and seagrasses, respectively, could be achieved by 2050. Further, protection and restoration can be complementary, as protection prevents losses that would otherwise occur post-2050, highlighting the importance of implementing protection measures. Our findings provide the scientific evidence required for setting strategic and ambitious targets to inspire significant global investment and effort in mangrove and seagrass conservation.
Buelow CA, Connolly RM, Turschwell MP, Adame MF, Ahmadia GN, Andradi-Brown DA, Bunting P, Canty SWJ, Dunic JC, Friess DA, Lee SY, Lovelock CE, McClure EC, Pearson RM, Sievers M, Sousa AI, Worthington TA, Brown CJ (2022). Ambitious global targets for mangrove and seagrass recovery. Current Biology
Seagrass meadows are threatened by multiple pressures, jeopardizing the many benefits they provide to humanity and biodiversity, including climate regulation and food provision through fisheries production. Conservation of seagrass requires identification of the main pressures contributing to loss and the regions most at risk of ongoing loss. Here, we model trajectories of seagrass change at the global scale and show they are related to multiple anthropogenic pressures but that trajectories vary widely with seagrass life-history strategies. Rapidly declining trajectories of seagrass meadow extent (>25% loss from 2000 to 2010) were most strongly associated with high pressures from destructive demersal fishing and poor water quality. Conversely, seagrass meadow extent was more likely to be increasing when these two pressures were low. Meadows dominated by seagrasses with persistent life-history strategies tended to have slowly changing or stable trajectories, while those with opportunistic species were more variable, with a higher probability of either rapidly declining or rapidly increasing. Global predictions of regions most at risk for decline show high-risk areas in Europe, North America, Japan, and southeast Asia, including places where comprehensive long-term monitoring data are lacking. Our results highlight where seagrass loss may be occurring unnoticed and where urgent conservation interventions are required to reverse loss and sustain their essential services.
Turschwell MP, Connolly RM, Dunic JC, Sievers M, Buelow CA, Pearson RM, Tulloch VJD, Cote IM, Unsworth RKF, Collier CJ, Brown CJ (2021). Anthropogenic pressures and life history predict trajectories of seagrass meadow extent at a global scale. PNAS 118, e2110802118.
Biofouling of ship hulls is one of the most important vectors for the transfer of aquatic invasive species. These species cause widespread impacts to native environments and ecological communities, in addition to imposing financial costs for industry. Targeted surveillance and effective adaptive management require knowledge on the likelihood of new introductions of non-indigenous species (NIS). We develop a model of the likelihood of introduction and invasion of NIS for the port of Arzew (Algeria), based on the length of stay of vessels in the ports of call, the latitude of these ports, the geographical distance from the port of Arzew, ship’s speed, effectiveness of the antifouling system and antifouling strategy used in port of origin. We identified areas that represent a source of high risk species invasion, according to the environmental similarity of the ports of origin with the Arzew port using the Mahalanobis distance. We show that over one year, 738 trips have been made at the port of Arzew, inflicting a very high risk of invasion, in particular from six coastal ecoregions, (the Western Mediterranean ecoregion, the Northern and Central Red Sea, the South European Atlantic Shelf, the Ionian Sea ecoregion, the North Sea, and the Aegean Sea). These results can be used for invasive species management purposes, such as: the application of specific regulations to high-risk vessels and ports in order to minimize the transfer of these species. The methods and models developed here are transferable to any region around the world with similar data availability.
Kacimi A, Bouda A, Sievers M, Bensari B, Houma F, Nacef L, Bachari NEI (2021). Modeling the risk of introducing non-indigenous species through ship hull biofouling: case study of Arzew port (Algeria). Management of Biological Invasions 12, 1012-1036.
Global-scale conservation initiatives and policy instruments rely on ecosystem indicators to track progress towards targets and objectives. A deeper understanding of indicator interrelationships would benefit these efforts and help characterize ecosystem status. We study interrelationships among 34 indicators for mangroves, saltmarsh, and seagrass ecosystems, and develop data-driven, spatially explicit typologies of coastal wetland status at a global scale. After accounting for environmental covariates and gap-filling missing data, we obtained two levels of clustering at 5 and 18 typologies, providing outputs at different scales for different end users. We generated 2,845 cells (1° (lat) × 1° (long)) globally, of which 29.7% were characterized by high land- and marine-based impacts and a high proportion of threatened species, 13.5% by high climate-based impacts, and 9.6% were refuges with lower impacts, high fish density and a low proportion of threatened species. We identify instances where specific actions could have positive outcomes for coastal wetlands across regions facing similar issues. For example, land- and marine-based threats to coastal wetlands were associated with ecological structure and function indicators, suggesting that reducing these threats may reduce habitat degradation and threats to species persistence. However, several interdimensional relationships might be affected by temporal or spatial mismatches in data. Weak relationships mean that global biodiversity maps that categorize areas by single indicators (such as threats or trends in habitat size) may not be representative of changes in other indicators (e.g., ecosystem function). By simplifying the complex global mosaic of coastal wetland status and identifying regions with similar issues that could benefit from knowledge exchange across national boundaries, we help set the scene for globally and regionally coordinated conservation.
Sievers M, Brown CJ, Buelow CA, Pearson RM, Turschwell MP, Adame MF, Griffiths L, Holgate B, Rayner TS, Tulloch VJD, Chowdhury MR, zu Ermgassen PS, Lee SY, Lillebø AI, Mackey B, Maxwell PS, Rajkaran A, Sousa AI, Connolly RM (2021). Global typologies of coastal wetland status to inform conservation and management. Ecological Indicators 131, 108141.
Surface-based cages are the dominant production technology for the marine finfish aquaculture industry. However, issues such as extreme weather events, poor environmental conditions, interactions with parasites, and conflicts with other coastal users are problematic for surface-based aquaculture. Submerged cages may reduce many of these problems and commercial interest in their use has increased. However, a broad synthesis of research into the effects of submerged culture on fish is lacking. Here, we review the current status of submerged fish farming worldwide, outline the biological challenges that fish with fundamentally different buoyancy control physiologies face in submerged culture, and discuss production benefits and problems that might arise from submerged fish farming. Our findings suggest that fish with closed swim bladders, and fish without swim bladders, may be well-suited to submerged culture. However, for fish with open swim bladders, such as salmonids, submergence is more complex as they require access to surface air to refill their swim bladders and maintain buoyancy. Growth and welfare of open swim bladder fish can be compromised by submergence for long periods due to complications with buoyancy regulation, but the recent addition of underwater air domes to submerged cages can alleviate this issue. Despite this advance, a greater understanding of how to couple advantageous environmental conditions with submerged culture to improve fish growth and welfare over the commercial production cycle is required if submerged cages are to become a viable alternative to surface-based cage aquaculture.
Sievers M, Korsøen Ø, Warren-Myers F, Oppedal F, Macaulay G, Dempster T (in press). Submerged cage aquaculture of marine fish: a review of the biological challenges and opportunities. Reviews in Aquaculture.