Through the years, research has described the importance of community-based approaches in the management of coastal and marine ecosystems. Coastal and marine issues are multifaceted and require place-specific approaches developed in partnership with vulnerable communities who are impacted by environmental stressors. Place-based conservation, a management approach that focuses on unique, place-specific characteristics, and other similar methods. It considers the need to integrate human dimensions and location-centered approaches, which are often lacking in typical natural resource management. Meaningful engagement with underrepresented communities can holistically account for socioeconomic factors and cultural knowledge that inform best management practices. As the health of marine and coastal ecosystems is linked with environmental quality and local livelihoods, engaging practitioners with knowledge of these systems can support science and trust in environmental management. This article discusses the importance of community-based research, local insight, various examples of successful management, and culturally relevant knowledge to advance sustainable place-based conservation.

The trace metal iron (Fe) is an essential micronutrient that controls phytoplankton productivity, which subsequently affects organic matter cycling with feedback on the cycling of macronutrients. Along the continental margin of the US West Coast, high benthic Fe release has been documented, in particular from deep anoxic basins in the Southern California Borderland. However, the influence of this Fe release on surface primary production remains poorly understood. In the present study from the Santa Barbara Basin, in situ benthic Fe fluxes were determined along a transect from shallow to deep sites in the basin. Fluxes ranged between 0.23 and 4.9 mmol m ⁻² d ⁻¹ , representing some of the highest benthic Fe fluxes reported to date. To investigate the influence of benthic Fe release from the oxygen-deficient deep basin on surface phytoplankton production, we combined benthic flux measurements with numerical simulations using the Regional Ocean Modeling System coupled to the Biogeochemical Elemental Cycling (ROMS-BEC) model. For this purpose, we updated the model Fe flux parameterization to include the new benthic flux measurements from the Santa Barbara Basin. Our simulations suggest that benthic Fe fluxes enhance surface primary production, supporting a positive feedback on benthic Fe release by decreasing oxygen in bottom waters. However, a reduction in phytoplankton Fe limitation by enhanced benthic fluxes near the coast may be partially compensated for by increased nitrogen limitation further offshore, limiting the efficacy of this positive feedback.

Methylotrophic methanogenesis in the sulfate reduction zone of coastal and marine sediments couples with anaerobic methane oxidation (AOM), forming the cryptic methane cycle. This study provides evidence of cryptic methane cycling in the sulfate-reducing zone across a land-ocean transect of four stations—two brackish, one marine, and one hypersaline—within the Carpinteria Salt Marsh Reserve (CSMR), Southern California, USA. The top 20 cm of sediment from the transect underwent geochemical and molecular (16S rRNA) analyses, in-vitro methanogenesis incubations, and radiotracer incubations using ³⁵ S-SO ₄ , ¹⁴ C-mono-methylamine, and ¹⁴ C-CH ⁴ . Sediment methane concentrations were consistently low (3 to 28 µM) except at the marine station, where they increased with depth (max 665 µM). Methanogenesis from mono-methylamine was detected throughout the sediment at all stations with estimated rates ranging between 0.14 and 3.8 nmol cm ⁻³ d ⁻¹ . 16S rRNA analysis identified methanogenic archaea capable of producing methane from methylamines in sediment where methanogenesis was found to be active. Metabolomic analysis of porewater showed mono-methylamine was mostly undetectable (<3 µM) or present in trace amounts (<10 µM) suggesting rapid metabolic turnover. In-vitro methanogenesis incubations showed no linear methane buildup, suggesting a process limiting methane emissions. AOM activity, measured with ¹⁴ C-CH ₄ , overlapped with methanogenesis from mono-methylamine activity at all stations, with rates ranging from 0.03 to 19.4 nmol cm ⁻³ d ⁻¹ . Porewater geochemical analysis showed the CSMR sediments are rich in sulfate and iron. Porewater sulfate concentrations (9–91 mM) were non-limiting across the transect, which support members of sulfate-reducing bacteria and likely responsible for sulfate reduction activity (1.5–2,506 nmol cm ⁻³ d ⁻¹ ) at all stations in the CSMR. Porewater sulfide and iron (II) profiles indicated that the sediment transitioned from a predominantly iron-reducing environment at the two brackish stations to a predominantly sulfate-reducing environment at the marine and hypersaline station. AOM activity was likely coupled to sulfate and possibly iron reduction, coinciding with the presence of anaerobic methanotrophs and bacteria involved in these reductions. 16S rRNA analysis identified anaerobic methanotrophs at the marine and hypersaline stations, where they coexisted with putative methanogens, suggesting both groups, or methanogens alone, may be involved in cryptic methane cycling, preventing significant methane buildup in the sulfate-reducing zone. Differences in rate constants from ¹⁴ C radiotracer incubations suggest a non-methanogenic process oxidizing mono-methylamine to inorganic carbon, likely mediated by sulfate-reducing bacteria. Understanding the potential competition of sulfate reducers with methanogens for mono-methylamine needs further investigation as it might be another important process responsible for low methane emissions in salt marshes.

             Methane in anoxic marine sediments comes primarily from microbial methanogenesis. Methanogenesis is facilitated by groups of obligate anaerobic archaea and is the last step in carbon remineralization according to the redox cascade. Before the methane is emitted into the water column and ultimately the atmosphere, where is acts as a potent greenhouse gas, a large portion (~90%) of the methane is consumed by anaerobic oxidation of methane (AOM). In anoxic marine sediments AOM is typically mediated by a consortium of methanotrophic archaea and sulfate-reducing bacteria to oxidize methane to inorganic carbon within a sediment layer classically known as the sulfate-methane transition zone (SMTZ). Organic matter in sediments above the SMTZ is consumed by organoclastic sulfate reduction, which thermodynamically outcompetes methanogenesis for hydrogen and acetate. However, methanogenesis can persist in sulfate-reducing environments with non-competitive substrates such as methylamines, which are produced from the microbial degradation of glycine betaine and dimethylsulfoniopropionate. Methanogenesis from methylamine can directly fuel AOM, now known as the “cryptic methane cycle”, in sulfate-reducing sediments. The cryptic methane cycle above the SMTZ is still poorly understood. Here we will present our preliminary research that shows evidence of cryptic methane cycling in sulfate-reducing sediments of the organic-rich Santa Barbara Basin (SBB).            We sampled the top 10-15cm of sediments at 5 stations along a depth transect across the basin. Sediment samples were subjected to radioisotope incubations with 14C-methane, 14C-mono-methylamine, and 35S-sulfate, gas chromatography, and porewater geochemical and metabolomic analysis. Porewater methane concentrations ranged from 3 to 13 µM. Metabolomic analysis of porewater using nuclear magnetic resonance for mono-methylamine concentrations found evidence of mono-methylamine presence below the quantification limit (< 3 µM). Results from the radiotracer incubations with 14C-methane detected ex-situ AOM rates at all 5 stations, where the highest rates were found within the top 1 cm. Integrated AOM (0-11cm) activity decreased with station water depth. 14C-mono-methylamine incubations revealed concurrent methanogenesis and AOM from mono-methylamine in the presence of sulfate reduction at all 5 stations. These results indicate evidence of potential cryptic methane cycling near the sediment-water interface in the Santa Barbara Basin.

Dissolved oxygen (O ₂ ) has been declining in coastal and open‐ocean regions, including the Santa Barbara Channel (SBC) in the Southern California Borderland. While previous studies have investigated the biogeochemical consequences of declining O ₂ in the SBC, its spatial distribution and temporal variability in the region remain poorly characterized. Because O ₂ dynamics shape the cycles of redox‐sensitive elements such as iron (Fe), improved characterization is essential for understanding regional biogeochemistry. We integrate observations of dissolved O ₂ spanning 1985–2023 using Autonomous Underwater Vehicle Sentry and the Remotely Operated Vehicle Jason . This new data set provides the first spatially resolved characterization of dissolved O ₂ across the SBC and Santa Barbara Basin. Above the Basin's sill, O ₂ exhibits a vigorous seasonal cycle, with low concentrations during springtime upwelling superimposed on a long‐term declining trend linked to decadal variability. This contrasts with the seasonal cycle below the sill, where higher O ₂ concentrations are observed in spring, reflecting reoxygenation by intermittent flushing events, which have weakened and become less frequent over time. Severe hypoxia and anoxia are widespread in the deep Basin, punctuated by coherent pockets of oxygenated waters, likely the remnants of flushing events. By combining reconstructions of the O ₂ distribution with a benthic Fe flux parameterization, we estimate the release of ∼24,000 tons of Fe annually from the sediment—far exceeding the Fe requirements of net primary production in the region. Our study provides new insights into O ₂ dynamics and their implications for biogeochemistry in the SBC, with relevance to global coastal deoxygenation.