Publication Date:
2022-05-25
Description:
Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution May 1989
Description:
Deep-sea benthic communities dependent on chemosynthetic primary
production are associated with areas of active venting of chemically-modified
seawater. Patterns in the distribution of species that occur
at hydrothermal vents can be used to predict locations of the vent
sites. Patterns in the distributions of species among vents along ridge
segments are used to identify the spatial scales over which biological
and physical processes operate to control community composition. Within
a vent, a zonation in species distributions correlates with gradients of
temperature and water chemistry. Along a given ridge segment, vent
communities share the same species pool, but the relative abundance of
each species varies from one site to another. On a basin-wide scale,
the fauna of vent communities represent biological continua, where
gradual morphological and genetic differentiation in species is
correlated with increasing distance between vent sites. Differentiation
of distinctive faunals assemblages at vents occursat a global scale.
Populations of species at vents are established and maintained through
recruitment of larval stages. To study recruitment processes at vent
sites, slate panels were placed at and near vent sites on the seafloor
for varying lengths of time. Size distributions of animals on retrieved
panels suggest that recruitment is an intermittent or continuous process
rather than a single episodic event. Recruitment of vent-associated
species was greater on panels placed within vent communities compared to
panels placed adjacent to these communities, a pattern consistent with
the observed maintenance of communities in discrete regions of
hydrothermal flux.
The trophic structure of chemosynthetic communities can be complex.
Primary production by chemoautotrophic bacteria can take place within
host tissues of some invertebrates as well as on surfaces and in the
water column and subsurface conduits. Carbon and nitrogen isotopic
compositions of host tissues can be used to demonstrate the dependence
of symbiont species on chemosynthetically-derived organic material.
From the patterns in the isotopic compositions of vent and seep
symbionts, potential sources of inorganic carbon are identified. Deep-water
dissolved inorganic carbon serves as a large, isotopically
buffered pool of inorganic carbon used by tubeworms and bivalves at
hydrothermal communities of Juan de Fuca, Gorda, Guaymas Basin, East
Pacific Rise, Galapagos, and Marianas vents. Variability in tubeworm
carbon isotopic compositions at seeps may be attributed to significant
contributions of isotopically variable DIC in seep effluents. Isotopic
techniques are also used to explore trophic relationships among a
variety of heterotrophic and symbiont-containing fauna at Hanging
Gardens on the East Pacific Rise and at Marianas vents. Carbon isotopic
measurements suggest that free-living bacteria are important sources of
food at both sites. Nitrogen isotopic analyses show that the Marianas
community may be simpler in trophic structure than the Hanging Gardens
community. The biomass of most known vent sites is conspicuously
dominated by large invertebrates with symbiotic bacteria. At vent sites
on the Mid-Atlantic Ridge, large swarms of shrimp dominate the biomass.
There is no evidence for endosymbionts in these shrimp, based on
analyses of morphology, stable isotopes, lipopolysaccharides and
ribulose- l, 5-bisphosphate carboxylase activity. Instead, the shrimp
appear to be normal heterotrophs, grazing on free-living microorganisms
associated with black smoker chimneys. High bacterial productivity
within the sulfide matrix of the chimneys must be required to sustain
the shrimp populations.
Hydrothermal vent environments exhibit some of the most extreme
gradients of temperature and chemistry found in the biosphere. Many of
the animals that colonize vent sites exhibit adaptations that allow them
to exist in such an unusual environment. A novel eye in shrimp from
Mid-Atlantic Ridge vents is described. The eye, comprised of a pair of
large organs within the cephalothorax, contains a visual pigment but
lacks image-forming optics. The eye appears to be adapted for detection
of low-level illumination and is suggested to have evolved in response
to a source of radiation associated with the environment of hydrothermal
vents. An electronic camera was used to detect light emitted from high-temperature
(350°C) plumes that rise from the orifice of black smoker
chimneys on the Endeavour Segment of the Juan de Fuca Ridge.
Calculations suggest that thermal radiation from hot water may account
for most of the light detected and that this light may be sufficient for
geothermally-drive photosynthesis by bacteria.
Description:
Portions of this dissertation were supported by grants from NSF, ONR, Sea Grant, and the WHOI Ocean Ventures Fund, by the WHOI Education Office, the WHOI Biology Department, and an NSF graduate fellowship.
Keywords:
Deep-sea ecology
;
Hydrothermal vent animals
;
Atlantis II (Ship : 1963-) Cruise
Repository Name:
Woods Hole Open Access Server
Type:
Thesis
Format:
10047903 bytes
Format:
application/pdf
Permalink
