Marine epiphytic diatoms: a review of environmental controls and ecosystem roles

The intricate relationships within coastal ecosystems are increasingly revealing themselves as vital components of ocean health, and a recent review highlights a particularly fascinating, yet often overlooked, element: epiphytic diatoms. These microscopic algae, colonizing the surfaces of marine macrophytes like seagrasses and macroalgae, represent a significant, and largely unexplored, facet of coastal microbenthic communities. The review synthesizes current understanding of their ecological roles and environmental controls, demonstrating their influence extends beyond simple primary production. This aligns with our ongoing focus on understanding the complex interplay of species within coastal zones, as exemplified by our previous coverage of [Wild-harvesting of the fucoid Fucus vesiculosus (Phaeophyceae) at an active oyster aquaculture site], which underscores the potential of macroalgae as a sustainable resource and the importance of understanding their interactions with other organisms. Similarly, the importance of habitat utilization, as detailed in [Spatial and temporal use of a tropical nursery habitat by juvenile blacktip sharks (Carcharhinus limbatus)], highlights the interconnectedness of different trophic levels within coastal ecosystems, a dynamic that epiphytic diatoms significantly influence.

The study’s emphasis on the interplay between biotic and abiotic factors shaping diatom assemblages is particularly insightful. While salinity, nutrient availability, and hydrodynamics predictably exert influence, the review rightly highlights the often-subtle but crucial role of host characteristics – morphological traits, leaf turnover rates, and even biochemical interactions – in dictating diatom colonization. The observed spatial and temporal variability, driven by seasonal cycles and host phenology, suggests a level of ecological complexity that demands further investigation. The identification of dominant genera like *Cocconeis* and their specific ecological strategies linked to substrate type and environmental conditions provides a valuable framework for future research. Furthermore, the classification of growth forms (adnate, erect, motile) as functional adaptations to host surfaces speaks to the evolutionary pressures shaping these microscopic communities. This research supports the need for integrated data ecosystems to effectively monitor and interpret these complex biological responses to environmental change.

Beyond their role as primary producers and trophic resources, the review positions epiphytic diatoms as sensitive bioindicators. Shifts in assemblage composition can act as early warning signals for changes in nutrient loading, hydrological regimes, and overall habitat degradation, demonstrating their potential as a valuable tool for biomonitoring. This is a crucial point, particularly as coastal ecosystems face increasing pressures from anthropogenic activities. The ability to detect subtle changes in these diatom communities could provide an empirical basis for informed management decisions, moving beyond broad assessments to more targeted and effective conservation strategies. Our own explorations of coastal dynamics, such as the [Numerical simulation of sediment transport characteristics under tidal action in the Qiantang estuary], also emphasize the need for robust monitoring systems to understand and predict the impacts of environmental change.

The authors’ conclusion regarding the relative scarcity of research on epiphytic diatom assemblages, particularly concerning functional traits and large-scale biogeographic patterns, serves as a clear call to action. While the review provides a comprehensive overview of current knowledge, significant gaps remain. Addressing these gaps will require longitudinal studies employing validated methodologies to track assemblage changes across diverse coastal environments. A key question moving forward is: how can we leverage advancements in remote sensing and molecular techniques to develop a real-time, high-resolution understanding of epiphytic diatom dynamics across broad geographic scales, ultimately strengthening our capacity for ocean intelligence and proactive stewardship?