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.
Submerged aquatic vegetation (SAV; e.g. seagrasses, macroalgae), forms key habitats in shallow coastal systems that provide a plethora of ecosystem services, including coastal protection, climate mitigation and supporting fisheries production. Light limitation is a critical factor influencing the growth and survival of SAV, thus it is important to understand how much light SAV needs, and receives, to effectively assess the risk that light limitation poses. Light monitoring is commonly used to inform environmental decision making to minimise loss of SAV habitat, but the temporal and spatial extent of monitoring is often limited by cost and logistical difficulties. An ability to remotely estimate light across different locations can therefore improve the conservation and management of SAV habitats. Here we combine an extensive monitoring program with publicly available data and machine learning to develop a model that estimates the light reaching submerged seagrasses in a shallow subtropical embayment in southern Queensland, Australia. Our model accurately predicts the intensity of photosynthetically active radiation (PAR) reaching the canopy of SAV from entirely remotely available data. The best performing model predicted light intensity with >99% at the management relevant daily, and 14-day rolling average time resolutions. This model enables monitoring of light available to SAV without an ongoing need for in-water instruments, minimising cost and risk to personnel, and improving assessment speed. The technique can be applied to SAV management plans in shallow waters throughout the world, where suitable remote public data is available.
Pearson RM, Collier CJ, Brown CJ, Rasheed MA, Bourner J, Turschwell MP, Sievers M, Connolly RM (2021). Remote estimation of aquatic light environments using machine learning: A new management tool for submerged aquatic vegetation. Science of the Total Environment, 782:146886.
Brown CJ, Adame MF, Buelow CA, Frassl MA, Lee SY, Mackey B, McClure EC, Pearson RM, Rajkaran A, Rayner TS, Sievers M (2021). Opportunities for improving recognition of coastal wetlands in global ecosystem assessment frameworks. Ecological Indicators, 126:107694.
Humans are altering marine ecosystems at unprecedented rates, and these changes can result in animals selecting poor-quality habitats if the cues they use become misleading. Such “ecological traps” increase extinction risk, reduce ecosystem resilience, and are a consequence of human-induced rapid environmental change. Although there is growing evidence for traps impacting terrestrial species, the phenomenon has so far received little attention from marine scientists. To explore why so few studies have attempted to identify traps in the ocean, we conducted a literature review of the major drivers of marine environmental change to determine how their impacts on habitat choice and species fitness are being assessed. From this we summarize the current evidence for marine traps, present case studies to show why the phenomenon is potentially common in the ocean, highlight ways to advance awareness and understanding of traps, and demonstrate how this information can help improve management of marine environments.