362
displayed abnormal behaviors and colors in 2010 (White et al. 2012b), and some
ophiuroids left their coral host between 2010 and 2011, which is also unusual as
individuals from this species rarely move away from their host (Girard et al. 2016).
However, these negative effects of the spill on ophiuroids did not persist after 2011.
Using images collected as part of the long-term monitoring program, a study showed
that A. clavigerum had a beneficial effect on coral recovery (Girard et al. 2016).
Corals associated with ophiuroids were less impacted than corals without ophiuroid
associates, and ophiuroids facilitated the recovery of branches in their vicinity from
both impact and hydroids colonization. A. clavigerum likely removes particles
depositing on coral branches and may also prevent the settlement of epibionts such
as hydroids (Girard et al. 2016). To date, the potential effects of the DWH on other
coral associates have not been characterized.
22.3 Soft-Bottom Habitats
About 70% of the Earth is covered by ocean, and about 65% is covered by deep-sea
benthic habitat, making it one of the largest habitats on Earth. It is well known that
deep-sea sediments are reservoirs of marine biodiversity in many places of the
world. The organisms in the sediments are composed primarily of two groups of
benthic invertebrates: the smaller meiofauna and larger macrofauna. The distinction
between, and definition of, the two groups is said to be operational because it is
based on size (Montagna et al. 2016). Macrofauna are retained on a 300 μm sieve,
and meiofauna pass through a 300 μm sieve and are retained on a 45 μm sieve.
However, there are also many taxonomic differences between the two groups.
Meiofauna are phyletically diverse (Fig. 22.2), and many of the phyla only occur in
marine sediment habitats. However, the meiofauna community is dominated by just
two taxa: the Nematoda and the Harpacticoida (an order of Crustacea). While most
phyla have representatives in the deep-sea macrofauna, just three phyla make up the
bulk of organisms found as infauna: Polychaeta, Crustacea, and Mollusca (Fig. 22.3).
These are the worms, shrimp-like organisms, and the hard-shelled clams and snails
familiar to all.
The diversity of infauna that live in sediments has been used as a sensitive bioindicator in many ecological health studies and in many different contexts. The reason
diversity is an important indicator of change is simple: during a disturbance or exposure to a toxic material, the sensitive species will be lost or disappear entirely, and
the tolerant species will remain or even increase. Thus, the ecological model for
disturbance detection is a loss of biodiversity and sometimes an increase in abundance of the “weedy” species. This is the basic approach used to assess the ecological health of all benthic communities and was applied to the GoM as well.
P. A. Montagna and F. Girard
displayed abnormal behaviors and colors in 2010 (White et al. 2012b), and some
ophiuroids left their coral host between 2010 and 2011, which is also unusual as
individuals from this species rarely move away from their host (Girard et al. 2016).
However, these negative effects of the spill on ophiuroids did not persist after 2011.
Using images collected as part of the long-term monitoring program, a study showed
that A. clavigerum had a beneficial effect on coral recovery (Girard et al. 2016).
Corals associated with ophiuroids were less impacted than corals without ophiuroid
associates, and ophiuroids facilitated the recovery of branches in their vicinity from
both impact and hydroids colonization. A. clavigerum likely removes particles
depositing on coral branches and may also prevent the settlement of epibionts such
as hydroids (Girard et al. 2016). To date, the potential effects of the DWH on other
coral associates have not been characterized.
22.3 Soft-Bottom Habitats
About 70% of the Earth is covered by ocean, and about 65% is covered by deep-sea
benthic habitat, making it one of the largest habitats on Earth. It is well known that
deep-sea sediments are reservoirs of marine biodiversity in many places of the
world. The organisms in the sediments are composed primarily of two groups of
benthic invertebrates: the smaller meiofauna and larger macrofauna. The distinction
between, and definition of, the two groups is said to be operational because it is
based on size (Montagna et al. 2016). Macrofauna are retained on a 300 μm sieve,
and meiofauna pass through a 300 μm sieve and are retained on a 45 μm sieve.
However, there are also many taxonomic differences between the two groups.
Meiofauna are phyletically diverse (Fig. 22.2), and many of the phyla only occur in
marine sediment habitats. However, the meiofauna community is dominated by just
two taxa: the Nematoda and the Harpacticoida (an order of Crustacea). While most
phyla have representatives in the deep-sea macrofauna, just three phyla make up the
bulk of organisms found as infauna: Polychaeta, Crustacea, and Mollusca (Fig. 22.3).
These are the worms, shrimp-like organisms, and the hard-shelled clams and snails
familiar to all.
The diversity of infauna that live in sediments has been used as a sensitive bioindicator in many ecological health studies and in many different contexts. The reason
diversity is an important indicator of change is simple: during a disturbance or exposure to a toxic material, the sensitive species will be lost or disappear entirely, and
the tolerant species will remain or even increase. Thus, the ecological model for
disturbance detection is a loss of biodiversity and sometimes an increase in abundance of the “weedy” species. This is the basic approach used to assess the ecological health of all benthic communities and was applied to the GoM as well.
P. A. Montagna and F. Girard