Short-term response of benthic foraminifera to fine-sediment depositional events simulated in microcosm
<p>A microcosm experiment was designed to describe how benthic foraminifera react to fine-sediment deposits varying in frequency and intensity as they may occur regularly or occasionally in coastal benthic environments, caused by discharges from (e.g.) river flooding, tidewater glacier melting...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2023-08-01
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| Series: | Biogeosciences |
| Online Access: | https://bg.copernicus.org/articles/20/3329/2023/bg-20-3329-2023.pdf |
| Summary: | <p>A microcosm experiment was designed to describe how benthic foraminifera
react to fine-sediment deposits varying in frequency and intensity as they
may occur regularly or occasionally in coastal benthic environments, caused
by discharges from (e.g.) river flooding, tidewater glacier melting in polar
regions, or diverse anthropic activities linked to harbour or watershed
management. The influence of seabed burial resulting from these events on
the ecology of benthic ecosystems is often overlooked, and the resilience of
benthic communities is poorly known. During a 51 d long experiment, a
typical northeastern Atlantic intertidal foraminiferal community, mainly
represented by <i>Ammonia confertitesta</i> and <i>Haynesina germanica</i> species, was subjected to two kinds of sedimentary
disturbance: (1) a one-time high-volume (OHV) deposit, i.e. sediment about 3 cm thick was added at one time at the beginning of the experiment; and (2) frequent low-volume (FLV) deposits, i.e. sediment about 0.5 cm thick was added each week for 4 weeks. The geochemical environment (e.g. dissolved oxygen penetration in the
sediment, salinity, temperature, and nutrient content in the supernatant
water) was monitored to follow the microcosm steady state before and during
the experiment. In both disturbed microcosms, <i>H. germanica</i> showed a significant linear
decrease in abundance during the experiment, while the total abundance of
foraminifera was significantly affected only by the OHV treatment,
suggesting a stronger effect of a single thick deposit on standing stocks
and biodiversity compared to frequent low-volume sediment supplies. Concerning the
vertical migration of foraminifera after sedimentary disturbances, the two
dominant species moved upwards to the water–sediment interface with
migration speeds estimated to be 0.41 and 0.47 mm h<span class="inline-formula"><sup>−1</sup></span> respectively for <i>A. confertitesta</i> and <i>H. germanica</i>. In
the FLV treatment, the resilient state was already reached within 1 d
following a low-thickness burial, while in the OHV, it was achieved between 1
and 7 d after the 3 cm thick deposit. These results suggest that
foraminifera can migrate rapidly after a sedimentary burial to recover their
preferential life position under the new sediment–water interface, but in the
case of an abrupt thick burial, several days are needed to reach a resilient
state.</p> |
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| ISSN: | 1726-4170 1726-4189 |