Sediment tolerance mechanisms identified in sponges using advanced imaging techniques.

Area of Science:

• Marine Biology
• Ecology
• Zoology

Background:

• Filter-feeding sponges are vulnerable to increased suspended sediment loads from terrestrial runoff, dredging, and resuspension events.
• Elevated sediment concentrations can reduce light intensity and smother sponges, impacting their survival and function.

Purpose of the Study:

• To investigate the response mechanisms of the sponge Ianthella basta to acute and chronic exposure to increased suspended sediment loads.
• To understand how sponges cope with sediment stress through various physiological and structural adaptations.

Main Methods:

• Ianthella basta was exposed to elevated suspended sediment concentrations, deposition, and light attenuation for 48 hours (acute) and 4 weeks (chronic).
• Sponge tissues were examined using 3D X-ray microscopy and scanning electron microscopy (SEM) to visualize response mechanisms.

Main Results:

• Acute exposure led to rapid sediment accumulation, fully removed within three days.
• Chronic exposure resulted in longer sediment removal times (>2 weeks), tissue regression, and a smaller aquiferous system.
• Ianthella basta demonstrated a multilevel sediment rejection system, including mucus production, particle exclusion, oscula closure, and tissue regression.

Conclusions:

• Ianthella basta employs a combination of active and passive mechanisms to reject and eliminate sediment, enhancing its resilience.
• These sediment stress responses allow sponges to tolerate variable and high sediment loads from both natural and anthropogenic sources.
• Understanding these mechanisms is crucial for assessing the impact of environmental changes on sponge populations.