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Eric
Borneman
Editor's Note:
For many years, little was known of viruses
in marine systems. Recently, the technology has become available
to begin probing ocean waters for viruses. It is now known
they are highly abundant and represent a major source of mortality
to phytoplankton. Also recently published is the finding of
viruses in bleached corals.
Seymour JR, Patten N, Bourne DG, Mitchell
JG. 2005. Spatial dynamics of virus-like particles and heterotrophic
bacteria within a shallow coral reef system. Mar Ecol Prog
Ser 288: 1-8.
Abstract:
Variations in the abundance and community
characteristics of virus-like particles (VLP) and heterotrophic
bacteria within a shallow, near-shore coral reef were determined
using flow cytometric analysis. Mean concentrations of 6.5
× 105 and 1.3 × 105 ml-1 were observed for VLP
and bacterioplankton, respectively, although concentrations
of both populations varied significantly (p < 0.05) between
4 distinct reef water types. Significant (p < 0.05) variability
in the percentage of high DNA (HDNA) bacteria, applied here
as an estimate of the proportion of active bacterial cells,
and the virus:bacteria ratio (VBR) was also observed between
different reef water types. Microscale profiles were taken
in the 12 cm layer of water directly above the surface of
coral colonies to determine the small-scale spatial relationships
between coral colonies and planktonic microbial communities.
Across these profiles, mean changes of 2- and 3.5-fold were
observed for bacterioplankton and VLP communities, respectively,
with VLP abundance positively correlated to bacteria in 75%
of profiles. Bacterial and VLP abundance, percentage of HDNA
bacteria, and VBR all generally exhibited increasing trends
with proximity to the coral surface. VLP abundance was significantly
higher (p < 0.05) in the 4 cm closest to the coral surface,
and the VBR was higher at the coral surface than in any other
zone. The patterns observed here indicate that VLP represent
an abundant and dynamic community within coral reefs, are
apparently coupled to the spatial dynamics of the bacterioplankton
community, and may consequently significantly influence nutrient
cycling rates and food-web structure within coral reef ecosystems.
Wilson WH, Dale AL, Davy JE, Davy SK.
2005. An enemy within? Observations of virus-like particles
in reef corals. Coral Reefs 24: 145-148.
No abstract.
Wilson WH, Francis I, Ryan K, Davy SK.
2001. Temperature induction of viruses in symbiotic dinoflagellates.
Aquat Microb Ecol 25: 99-102.
Abstract:
Bleaching manifests itself as a loss of
symbiotic dinoflagellates (zooxanthellae) and/or chlorophyll
from a variety of symbiotic hosts, including corals and sea
anemones. Bleaching is known to result from a range of environmental
stresses, the most significant of which is elevated temperature;
how these stresses elicit a bleaching response is currently
the focus of intense research. One consequence of environmental
stress that has yet to be considered is viral attack. Here,
we have isolated a transferable infectious agent believed
to be a virus, from zooxanthellae of the temperate sea anemone
Anemonia viridis. The infectious agent is induced by
elevated temperature. Once induced, the filterable agent can
be further propagated without heat induction, thus fulfilling
Koch's postulates. We propose that zooxanthellae harbor a
latent viral infection that is induced by exposure to elevated
temperatures. If such a mechanism also operates in the zooxanthellae
harbored by reef corals, and these viruses kill the symbionts,
then this could contribute to temperature-induced bleaching.
Breitbart M, Salamon P, Andresen B,
Mahaffy JM, Segall AM, Mead D, Azam F, and Rohwer F. 2002,
Proc Natl Acad Sci USA 99: 14250-14255.
Abstract:
Genomic analysis of uncultured marine viral
communities. Viruses are the most common biological entities
in the oceans by an order of magnitude. However, very little
is known about their diversity. Here, we report a genomic
analysis of two uncultured marine viral communities. Over
65% of the sequences were not significantly similar to previously
reported sequences, suggesting that much of the diversity
is previously uncharacterized. The most common significant
hits among the known sequences were to viruses. The viral
hits included sequences from all of the major families of
dsDNA tailed phages, as well as some algal viruses. Several
independent mathematical models based on the observed number
of contigs predicted that the most abundant viral genome comprised
2-3% of the total population in both communities, which was
estimated to contain between 374 and 7,114 viral types. Overall,
diversity of the viral communities was extremely high. The
results also showed that it would be possible to sequence
the entire genome of an uncultured marine viral community.
Ronald
L. Shimek, Ph. D.
Editor's Note:
If you ever wanted conclusive proof that the reef aquarium
hobby can have a deleterious effect on natural populations,
see these two articles. The first article showed that the
natural population of Banggai cardinalfish is very small and
localized.
The second article documented that as a minimum, 118,000
fish per month or 1,416,000 fish per year, were being collected
for the aquarium trade from these limited populations. The
authors conclude that this harvesting rate has already reduced
the populations throughout the region and the fish remaining
are now smaller than they had been previously.
It appears that the long-term effects of continued unregulated
harvesting will mean at least local population extinction
and may mean extinction of the species, probably in the not
too distant future unless action is taken to regulate the
fishery.
Bernardi G and A. Vagelli. 2004. Population
structure in Banggai cardinalfish, Pterapogon kauderni,
a coral reef species lacking a pelagic larval phase. Marine
Biology (2004) 145: 803-810.
Abstract:
Previous studies on two reef fish lacking
a pelagic larval phase (Acanthochromis polyacanthus
and Embiotoca jacksoni) revealed features that may
be characteristic of their lifestyle: (1) low levels of gene
flow, (2) frequent population bottlenecks, and (3) strong
phylogeographic breaks, all within their over 1,000 km coastal
geographic ranges. The present study tested the predictive
nature of these three characteristics in another species lacking
a pelagic larval stage, but with a very restricted distribution
(<10,000 km2). The Banggai
cardinalfish, Pterapogon kauderni (Koumans, 1933),
is a mouthbrooding species occurring in the Banggai Archipelago
(eastern Indonesia). Fish were captured in January and February
(2001, 2002). The mitochondrial control region of 122 individuals
from 22 locations was sequenced. Pterapogon kauderni
individuals clustered in two reciprocally monophyletic clades
corresponding to a southwestern population (restricted to
the southwest of Bangkulu Island) and all northern and eastern
populations, which included all the remaining samples. Data
were compatible with reduced gene flow and the presence of
severe bottlenecks; however, small sample sizes and limited
genetic variability in P. kauderni prevented a definitive
conclusion. Further studies using larger samples and more
rapidly evolving molecular markers may provide enough power
to conclusively test our hypothesis.
Lunn, K. E. and M.-A. Moreau. 2004.
Unmonitored trade in marine ornamental fishes: the case of
Indonesia's Banggai cardinalfish (Pterapogon kauderni).
Coral Reefs (2004) 23: 344-351.
Abstract:
Millions of coral reef fishes are collected
each year for sale on the international aquarium market. Several
marine ornamental species, including the Banggai cardinalfish,
are biologically unsuitable for large scale exploitation,
yet their trade continues largely unmonitored. With little
known about the Banggai cardinalfish or its trade, we interviewed
trade participants from north and central Sulawesi, Indonesia,
and documented the organization, scale, and price structure
of the species' local collection and sale. Interviews revealed
a large and growing commerce in Banggai cardinalfish, with
at least 118,000 fish per month being sold in the Banggai
region during the study period. Given the nature of the trade,
the species' restricted geographic range, its natural susceptibility
to exploitation, we propose long-term monitoring is needed
to safeguard Banggai cardinalfish populations and to serve
as a much-needed example for monitoring and managing other
marine ornamental fishes at risk of over-exploitation.
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