Learning from differences: Abiotic determinism of benthic communities in Northern Taiwan

Drivers of coastal benthic communities in a complex environmental setting

Analyzing the environmental factors affecting benthic communities in coastal areas is crucial for uncovering key factors that require conservation action. Here, we collected benthic and environmental (physical-chemical-historical and land-based) data for 433 transects in Taiwan. Using a k-means approach, five communities dominated by crustose coralline algae, turfs, stony corals, digitate, or bushy octocorals were first delineated. Conditional random forest models then identified physical, chemical, and land-based factors (e.g., light intensity, nitrite, and population density) relevant to community delineation and occurrence. Historical factors, including typhoons and temperature anomalies, had only little effect. The prevalent turf community correlated positively with chemical and land-based drivers, which suggests that anthropogenic impacts are causing a benthic homogenization. This mechanism may mask the effects of climate disturbances and regional differentiation of benthic assemblages. Consequently, management of nutrient enrichment and terrestrial runoff is urgently needed to improve community resilience in Taiwan amidst increasing challenges of climate change.

Coral transplantation in urban environments: Insights from colony survival and growth on artificial frames versus the seabed

Urban and green transitions require infrastructures that can cause pressure on coastal ecosystems. In northern Taiwan, plans to convert an oil-fired power plant to gas would necessitate a port terminal construction, threatening nearby corals and marine life. To mitigate construction impacts, the relocation of affected corals was proposed. We conducted a transplantation study, prior to such a large-scale coral relocation, to assess its feasibility and to identify potential risks associated with the marginal location of northern Taiwan for tropical corals. Five coral species, representative of the different ecological strategies, were selected. We used two methods (artificial frames and seabed cementation) to transplant 246 colony fragments to two pre-selected sites. Over a year, we monitored fragment survival and growth, in parallel with environmental conditions. We found that survival and growth were significantly influenced by transplantation methods, sites, and species. The difference between methods revealed biotic (predation by corallivorous snails) and abiotic (mechanical damage by waves) factors affecting coral survival and growth. Acropora species exhibited high growth, but also high mortality, consistent with their known ecology. Other species presented slower growth but higher survival. One site provided a better environment for corals, which we attributed to topography and reduced exposure. Overall, this study provides interesting insights into relocating corals in a high-latitude and urban coral ecosystem, highlighting risks related to mechanical damages and predation.