Environmental stressors, complex interactions and marine benthic communities' responses.

Area of Science:

• Marine ecology
• Environmental toxicology
• Ecosystem resilience

Background:

• Anthropogenic stressors increasingly impact marine ecosystems, affecting biodiversity and functions.
• Assessing cumulative stressor effects, including non-linear responses like synergies and antagonisms, is crucial but experimentally challenging.
• Previous studies often focus on single biological responses, limiting understanding of complex stressor interactions.

Purpose of the Study:

• To investigate the isolated and combined effects of warming, salinity variation, and nutrient enrichment on a bivalve assemblage.
• To assess impacts across multiple biological levels, including bivalve mortality, growth, shell mineralization, energy content, and microphytobenthos biomass.
• To understand how these effects change over time (one and three months) and identify stressor interactions.

Main Methods:

• A manipulative experiment exposing a bivalve assemblage to controlled levels of warming (+6 °C), salinity variation (freshwater pulses/presses), and nutrient enrichment (natural vs. enriched).
• Measurements included bivalve mortality, growth rates, shell mineralization, energy content, and microphytobenthos biomass.
• Data were analyzed to determine individual and combined stressor impacts and their temporal variation.

Main Results:

• Salinity variation and nutrient enrichment significantly impacted several measured variables, both individually and in combination.
• The effects of salinity and nutrient stressors varied considerably over the one- and three-month exposure periods.
• Warming (+6 °C) did not produce any significant effects on the measured bivalve or microphytobenthos responses.
• Antagonistic interactions between stressors were prevalent, influencing the overall biological responses.

Conclusions:

• Salinity and nutrient enrichment are key drivers of change in this bivalve assemblage, with effects modulated by time.
• Warming, under the tested conditions, did not significantly alter the measured biological responses.
• Understanding stressor interactions requires examining multiple biological responses and considering temporal dynamics to reveal complex ecological consequences.