Christopher R. Kelble

Future ocean conditions will likely alter habitat suitability for many species, potentially resulting in range shifts. Climate models simulate environmental conditions under climate scenarios and serve as a valuable tool for projecting future changes in habitat suitability. Here, we use ocean bottom temperature patterns from a multi-model ensemble mean of 6 Coupled Model Intercomparison Project (CMIP6) models for ‘low’, ‘medium’, and ‘high’ emission socioeconomic climate scenarios (SSP2-4.5, SSP3-7.0, SSP5-8.5) to estimate changes in thermal habitat availability for 6 commercially important fish species along the US Atlantic coast from 2015 to 2100. Thermal preferences were derived from survey data, and modeled bottom temperatures were adjusted to better reflect observed habitat conditions. Projections indicated declines in suitable thermal habitat for all species, although rates varied, with poleward shifts in northern range edges evident by the end of the century. Projected changes in suitable thermal habitat are likely to contribute to shifts in species distributions, which may require fisheries management bodies to co-develop strategies that address the reorganization of marine ecosystems under climate change. Enhancing model resolution and accounting for regional factors should significantly improve these predictions, allowing for the use of robust species distribution models.

Ecosystem-based fisheries management is a crucial advancement to address natural and anthropogenic stressors on marine ecosystems. Although there has been a shift toward more holistic management approaches over the past few decades, Fishery Management Councils still face challenges in implementing ecosystem-based strategies. Here, we present a case study on incorporating harmful algal blooms, known as red tides, into U.S. federal fisheries management on the West Florida Shelf. Red tides are first defined as a fishery ecosystem issue by outlining their ecological, economic, and societal impacts on the relevant fisheries. We then review the history of including red tides in the stock assessment process and how management actions have responded to episodic mortality attributed to devastating red tides. Fishery managers have encountered significant challenges when addressing red tides because the root causes are beyond fisheries management jurisdiction. The primary method to account for red tides in fisheries management has been to incorporate extra mortality in stock assessments. While integrating ecosystem information can reduce scientific uncertainty in stock assessments, the setting of catch limits also benefits from such information. Red tide-related management actions have been reactive, and frequent reversals of catch advice highlight the complexity of red tide impacts. The directionality of catch advice for Gulf groupers has been dependent upon additional information such as ecosystem modeling results and stakeholder observations. We offer a review of potential fishery management policy options that include, but are not limited to, the management of fishing mortality. We outline research recommendations to better characterize impacts and inform fisheries management’s response to red tides. Effective ecosystem-based fisheries management necessitates a clear definition of the problem, goals, expectations, metrics to measure progress, and a work plan that includes stakeholder engagement.

Ocean acidification and warming threaten marine life, yet the impact of these processes on microbes remains unclear. Here, we performed basin-scale DNA metabarcoding of prokaryotes (16S V4–V5) and protists (18S V9) in the Gulf of Mexico and applied generalized linear models to reveal group-specific environmental correlates of functionally diverse microbes. Models supported prior physiological trends for some groups, like positive temperature effects on SAR11 and SAR86, and a positive effect of pH on Prochlorococcus that implied a negative response to decreasing pH. New insights were revealed for protists, like Syndiniales and Sagenista (e.g., positive pH effects), which offset positive relationships with temperature and reinforced the importance of considering multiple stressors simultaneously. Indicator analysis revealed phytoplankton, like Ostreococcus sp. and Emiliania huxleyi , that were associated with more acidic waters and may reflect candidate indicators of ocean change. Our findings highlight the need for sustained microbial sampling in marine systems, with implications for carbon export, nutrient cycling, and ecosystem health.

Ocean acidification (OA) threatens coral reef persistence by decreasing calcification and accelerating the dissolution of reef frameworks. The carbonate chemistry of coastal areas where many reefs exist is strongly influenced by the metabolic activity of the underlying benthic community, contributing to high spatiotemporal variability. While characterizing this variability is difficult, it has important implications for the progression of OA and the persistence of the ecosystems. Here, we characterized the carbonate chemistry at 38 permanent stations located along 10 inshore‐offshore transects spanning 250 km of the Florida Coral Reef (FCR), which encompass four major biogeographic regions (Biscayne Bay, Upper Keys, Middle Keys, and Lower Keys) and four shelf zones (inshore, mid‐channel, offshore, and oceanic). Data have been collected since 2010, with approximately bi‐monthly periodicity starting in 2015. Increasing OA, driven by increasing DIC, was detected in the mid‐channel, offshore, and oceanic zones in every biogeographic region. In the inshore zone, however, increasing TA counteracted any measurable OA trend. Strong seasonal variability occurred at inshore sites and included periods of both exacerbated and mitigated OA. Seasonality was region‐dependent, with greater variability in the Lower and Middle Keys. Elevated pH and aragonite saturation states (Ω_Ar) were observed in the Upper and Middle Keys, which could favor reef habitat persistence in these regions. Offshore reefs in the FCR could be more susceptible to global OA by experiencing open‐ocean‐like water chemistry conditions. By contrast, higher seasonal variability at inshore reefs could offer a temporary OA refuge during periods of enhanced primary production.

Harmful algal blooms (HABs) caused by the dinoflagellate Karenia brevis on the West Florida Shelf have become a nearly annual occurrence causing widespread ecological and economic harm. Effects range from minor respiratory irritation and localized fish kills to large-scale and long-term events causing massive mortalities to marine organisms. Reports of hypoxia on the shelf have been infrequent; however, there have been some indications that some HABs have been associated with localized hypoxia. We examined oceanographic data from 2004 to 2019 across the West Florida Shelf to determine the frequency of hypoxia and to assess its association with known HABs. Hypoxia was present in 5 of the 16 years examined and was always found shoreward of the 50-meter bathymetry line. There were 2 clusters of recurrent hypoxia: midshelf off the Big Bend coast and near the southwest Florida coast. We identified 3 hypoxic events that were characterized by multiple conductivity, temperature, and depth (CTD) casts and occurred concurrently with extreme HABs in 2005, 2014, and 2018. These HAB-hypoxia events occurred when K. brevis blooms initiated in early summer months and persisted into the fall likely driven by increased biological oxygen demand from decaying algal biomass and reduced water column ventilation due to stratification. There were also four years, 2011, 2013, 2015, and 2017, with low dissolved oxygen located near the shelf break that were likely associated with upwelling of deeper Gulf of Mexico water onto the shelf. We had difficulty in assessing the spatiotemporal extent of these events due to limited data availability and potentially unobserved hypoxia due to the inconsistent difference between the bottom of the CTD cast and the seafloor. While we cannot unequivocally explain the association between extreme HABs and hypoxia on the West Florida Shelf, there is sufficient evidence to suggest a causal linkage between them.

Harmful algal blooms (HABs) caused by the dinoflagellate Karenia brevis on the West Florida Shelf have become a nearly annual occurrence causing widespread ecological and economic harm. Effects range from minor respiratory irritation and localized fish kills to large-scale and long-term events causing massive mortalities to marine organisms. Reports of hypoxia on the shelf have been infrequent; however, there have been some indications that some HABs have been associated with localized hypoxia. We examined oceanographic data from 2004 to 2019 across the West Florida Shelf to determine the frequency of hypoxia and to assess its association with known HABs. Hypoxia was present in 5 of the 16 years examined and was always found shoreward of the 50-meter bathymetry line. There were 2 clusters of recurrent hypoxia: midshelf off the Big Bend coast and near the southwest Florida coast. We identified 3 hypoxic events that were characterized by multiple conductivity, temperature, and depth (CTD) casts and occurred concurrently with extreme HABs in 2005, 2014, and 2018. These HAB-hypoxia events occurred when K. brevis blooms initiated in early summer months and persisted into the fall likely driven by increased biological oxygen demand from decaying algal biomass and reduced water column ventilation due to stratification. There were also four years, 2011, 2013, 2015, and 2017, with low dissolved oxygen located near the shelf break that were likely associated with upwelling of deeper Gulf of Mexico water onto the shelf. We had difficulty in assessing the spatiotemporal extent of these events due to limited data availability and potentially unobserved hypoxia due to the inconsistent difference between the bottom of the CTD cast and the seafloor. While we cannot unequivocally explain the association between extreme HABs and hypoxia on the West Florida Shelf, there is sufficient evidence to suggest a causal linkage between them.

The ecosystem‐based fisheries management (EBFM) framework has a solid theoretical justification and has been embraced in principle by many regions; yet, systematic implementation remains a challenge. In regions with strong governance, single‐species stock assessment and management has been successful in ending overfishing and maintaining stocks near levels that produce maximum catches. However, considering species in isolation and recognizing a limited set of management objectives leads to systemic inefficiencies, incentivizes waste and generates unintended consequences. To avoid undesirable outcomes, human values and needs must be positioned at the forefront of management, system‐level objectives must be identified, and management actions must be systematically evaluated to ensure they are contributing to those larger objectives. Such processes, when implemented transparently, will lead to reduced conflict and improved stakeholder support for governance and should greatly facilitate long‐term management. We argue here that, regardless of the management framework adopted, we inherently manage at the ecosystem level—albeit sometimes “blindly”—and that increased attention to ecosystem objectives and trade‐offs will improve management outcomes.