Benthic diatom diversity in microtidal mangrove estuaries.

Area of Science:

• Marine Ecology
• Benthic Ecology
• Microbial Ecology

Background:

• Mangrove ecosystems host diverse benthic communities, but their impact on microphytobenthos is not well understood.
• Microphytobenthos, particularly diatoms, are crucial primary producers in estuarine environments.
• Understanding diatom community structure in mangroves is key to assessing ecosystem health.

Purpose of the Study:

• To investigate the benthic diatom community structure in South African mangrove estuaries.
• To correlate diatom diversity and abundance with environmental factors like sediment organic content and clay fraction.
• To identify indicator species for assessing estuarine health and potential nutrient enrichment.

Main Methods:

• Sampling of benthic diatoms from 17 microtidal mangrove estuaries along the South African east coast.
• Analysis of sediment properties, including organic content and clay fraction.
• Community structure analysis using diversity indices (e.g., H') and identification of dominant diatom taxa.

Main Results:

• High sediment organic content and clay fraction in Avicennia marina and Rhizophora mucronata habitats supported diverse diatom communities (H' > 3).
• Unique species like Gyrosigma balticum were found, indicating specialized habitat requirements.
• Nutrient-tolerant species (e.g., Halamphora acutiuscula, Navicula spp.) dominated in certain estuaries, suggesting potential nutrient enrichment.

Conclusions:

• Mangrove habitat complexity provides crucial microrefugia for benthic diatom colonization.
• The presence of nutrient-tolerant diatom species can serve as an early warning for anthropogenic nutrient enrichment in otherwise pristine systems.
• This study highlights the importance of benthic diatoms as bioindicators of estuarine health in mangrove ecosystems.