In five summer cruises during the period 2000-2004, seventy-four box cores
were collected from eleven locations from the Mississippi Canyon (480- 2750m,
northern Gulf of Mexico), and an adjacent transect (336-2920) to understand the
community structure and trophic function of amphipods and for measuring the
bioaccumulation of polycyclic aromatic hydrocarbons, (PAHs). Amphipods were
discovered to be an important component of the macrofauna of the Mississippi Canyon
(40 % of the total faunal abundance). Seventy two species, belonging to nineteen
families, were collected from the study area with 61 species from the canyon and only
38 species from the non-Canyon transect. The head of the canyon (480m) was
dominated by dense mats (15,880 ind/m2) of a new amphipod (Ampelisca
mississippiana). The logarithm of the amphipod abundance decreased linearly with
depth. The species diversity (H`) exhibited a parabolic pattern with a maximum at
1100m. The differences in amphipod abundances and biodiversities were correlated with
the variation in the amount of available organic matter. The depression in diversity in the
canyon head is thought to be competitive exclusion resulting from the dominance by A.mississippiana, but the high species richness is presumed to be a function of the
structural complexity of the canyon.
Annual secondary production of A. mississippiana was 6.93 g dry wt m-2, based
on size-frequency method and corresponding to an estimated univoltine generation from
a regression model. The production/biomass ratio (P/B) was 3.11. Production of this
magnitude is comparable to shallow marine ampeliscids but are high for the depauperate
northern Gulf of Mexico.
The effect of the organic contaminants and the bioavailability to the amphipods
was determined through measuring the bioaccumulation of the PAHs. The distribution of
PAHs in sediments was different from the distribution in the organisms suggesting
preferential uptake/depuration or uptake from pore or bottom waters. The average
bioaccumulation factor (4.36 ± 2.55) and the biota sediment accumulation factor
(0.24±0.13) for the total PAHs by the ampeliscids were within the range reported for
other benthic invertebrates. The average bioaccumulation factors were highest for
dibenzothiophenes (up to 132) and alkylated PAHs and lowest for parent high molecular
weight PAHs.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-1356 |
| Date | 15 May 2009 |
| Creators | Soliman, Yousria Soliman |
| Contributors | Rowe, Gilbert T, Wade, Terry L. |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Dissertation, text |
| Format | electronic, application/pdf, born digital |
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