364
Department of the Interior is responsible for these studies. In June 2010, the
Minerals Management Service (MMS) was renamed the Bureau of Ocean Energy
Management, Regulation and Enforcement (BOEMRE). The current BOEMRE and
past MMS carried out two large-scale surveys of the deep GoM. The Northern Gulf
of Mexico Continental Slope Study (NGOMCSS) was carried out between 1983
and 1985 (Gallaway 1988; Pequengnat et al. 1990). The Deep Gulf of Mexico
Benthos (DGoMB) was carried out between 2000 and 2002 (Rowe and Kennicutt
2008, 2009). Both studies measured meiofauna and macrofauna infauna communities, megafauna, and a suite of other environmental physical-chemical variables in
water depths of 300 m–3000 m using a transect design that covered the western,
central, and eastern parts of the northern GoM. The DGoMB study also sampled the
Sigsbee Abyssal Plain.
In the NGOMCSS study, 98% of the meiofauna was found to be made up by
nematodes, harpacticoid copepods, nauplii, polychaetes, ostracods, and kinorynchs
in that order. Nematodes and copepods alone made up 77% of the individuals. For
macrofauna, 86% of the community was dominated by polychaetes, ostracods,
bivalves, tanaids, bryozoans, and isopods, respectively. Meiofauna abundances
ranged from 120,000 to 551,000 individuals/m
2
, and macrofauna abundances ranged
from 1560 to 8250 individuals/m
2
. The macrofauna was very diverse and dominated
by rarity because only 110 of 1212 species were represented by 10 or more individuals. However, very few of the species had existing names, and there was uncertainty about the taxonomy. The highest abundances for both groups were found in
the central transect and decreased with depth in all transects. Most species were
restricted to specific depth distributions, and there was more variability with depth
than there was among transects. There was a break with peak abundances and diversity in depths ranging from 500 m to 1000 m.
In the DGoMB study, 99% of the meiofauna were made up of nematodes, harpacticoid copepods, nauplii, polychaetes, kinorynchs, and ostracods in that order.
Nematodes and copepods alone made up 78% of the individuals. Meiofauna abundances ranged from 60,400 to 540,000 individuals/m
2
, and macrofauna abundances
ranged from 284 to 6400 individuals/m
2
. But there was one outlier, station MT1 at
the base of the Mississippi Trough that had an abundance of 20,700 individuals/m
2
.
The greater abundances in the Central Gulf resulted from the proximity to the
Mississippi River outflow (Baguley et al. 2006a). Canyon features in proximity of
Mississippi River outflow were found to greatly enhance meiofauna abundance.
Mississippi River outflow alters local sediment characteristics and interacts with
loop current eddies and dynamic slope topography to increase particulate organic
matter flux in the northeastern region, thus creating areas of higher than normal
meiofauna abundance. Meiofauna abundance was also related to water depth.
Harpacticoida were the only meiofauna species identified to the lowest taxonomic
level possible (Baguley et al. 2006b). Species richness declined linearly with
increasing depth and was highest at 1200 m.
For macrofauna, 86% of the community was dominated by polychaetes, ostracods, bivalves, tanaids, bryozoans, and isopods in that order. Not all macrofauna
species were identified to the lowest taxonomic level possible. Few of the deep-sea
P. A. Montagna and F. Girard
Department of the Interior is responsible for these studies. In June 2010, the
Minerals Management Service (MMS) was renamed the Bureau of Ocean Energy
Management, Regulation and Enforcement (BOEMRE). The current BOEMRE and
past MMS carried out two large-scale surveys of the deep GoM. The Northern Gulf
of Mexico Continental Slope Study (NGOMCSS) was carried out between 1983
and 1985 (Gallaway 1988; Pequengnat et al. 1990). The Deep Gulf of Mexico
Benthos (DGoMB) was carried out between 2000 and 2002 (Rowe and Kennicutt
2008, 2009). Both studies measured meiofauna and macrofauna infauna communities, megafauna, and a suite of other environmental physical-chemical variables in
water depths of 300 m–3000 m using a transect design that covered the western,
central, and eastern parts of the northern GoM. The DGoMB study also sampled the
Sigsbee Abyssal Plain.
In the NGOMCSS study, 98% of the meiofauna was found to be made up by
nematodes, harpacticoid copepods, nauplii, polychaetes, ostracods, and kinorynchs
in that order. Nematodes and copepods alone made up 77% of the individuals. For
macrofauna, 86% of the community was dominated by polychaetes, ostracods,
bivalves, tanaids, bryozoans, and isopods, respectively. Meiofauna abundances
ranged from 120,000 to 551,000 individuals/m
2
, and macrofauna abundances ranged
from 1560 to 8250 individuals/m
2
. The macrofauna was very diverse and dominated
by rarity because only 110 of 1212 species were represented by 10 or more individuals. However, very few of the species had existing names, and there was uncertainty about the taxonomy. The highest abundances for both groups were found in
the central transect and decreased with depth in all transects. Most species were
restricted to specific depth distributions, and there was more variability with depth
than there was among transects. There was a break with peak abundances and diversity in depths ranging from 500 m to 1000 m.
In the DGoMB study, 99% of the meiofauna were made up of nematodes, harpacticoid copepods, nauplii, polychaetes, kinorynchs, and ostracods in that order.
Nematodes and copepods alone made up 78% of the individuals. Meiofauna abundances ranged from 60,400 to 540,000 individuals/m
2
, and macrofauna abundances
ranged from 284 to 6400 individuals/m
2
. But there was one outlier, station MT1 at
the base of the Mississippi Trough that had an abundance of 20,700 individuals/m
2
.
The greater abundances in the Central Gulf resulted from the proximity to the
Mississippi River outflow (Baguley et al. 2006a). Canyon features in proximity of
Mississippi River outflow were found to greatly enhance meiofauna abundance.
Mississippi River outflow alters local sediment characteristics and interacts with
loop current eddies and dynamic slope topography to increase particulate organic
matter flux in the northeastern region, thus creating areas of higher than normal
meiofauna abundance. Meiofauna abundance was also related to water depth.
Harpacticoida were the only meiofauna species identified to the lowest taxonomic
level possible (Baguley et al. 2006b). Species richness declined linearly with
increasing depth and was highest at 1200 m.
For macrofauna, 86% of the community was dominated by polychaetes, ostracods, bivalves, tanaids, bryozoans, and isopods in that order. Not all macrofauna
species were identified to the lowest taxonomic level possible. Few of the deep-sea
P. A. Montagna and F. Girard