Rozan,
T.F., Taillefert, M., Trouwborst, R.E., Glazer, B.T., Ma, S.F., Herszage,
J., Valdes, L.M., Price, K.S. and G.W. Luther. 2002. Iron-sulfur-phosphorous
cycling in the sediments of a shallow coastal bay: Implications for
sediment nutrient release and benthic macroalgal blooms. Limnology and Oceanography 47(5): 1346-1354.
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This is a
rather interesting paper, even though the study was conducted
along the Delaware coast and the sediments may not
carbonate-based. The study investigated the seasonal changes in
iron (Fe), sulfur (S) and phosphorous (P) levels in the first 4 cm
(~1.5 inches) of sediment in a coastal embayment with residence
time of 100 days. It was found that redox conditions in the
sediments greatly affected the levels of these three elements in
the sediments, pore waters and overlying water. In the summer
months the sediments became reducing (anoxic), resulting in
release of P into the surface waters. These anoxic conditions are
due to the fact that the bays are considered eutrophic due to
nutrient run-off and phytoplankton increases in the summer with
increased light and temperatures. This results in an increase in
the decay of organic matter in the sediment and hence, lower oxygen levels.
This resulted in blooms of macroalgae throughout the bay. In the
fall the sediments became oxic again with an increase in redox,
and a decrease in soluble P. The reason for this release of P was
linked to an increased production of iron sulfides (both FeS and
FeS2) and a decrease in iron (III) oxides. In the fall
and winter, iron sulfide production is decreased and iron (III)
oxides increased. It was felt that perhaps iron (III) oxides acted
as a barrier to diffusive P flux. Most of the reactive P came from
that fraction of iron that was ascorbic acid soluble (ASC-Fe). The
associated production of H2S in the summer, not only
promoted the dissolution of solid iron (III) oxides but also the
removal of soluble Fe (II). Both of these actions enhanced soluble
phosphate cycling into the sediments and the overlying water.
It was also found
that the pH of the sediments decreased to 6.5 in the summer months. This
resulted in the greater production of H2S, which promoted the
dissolution of solid iron (III) oxides, and the removal of soluble Fe
(II), both of which enhance phosphate recycling in the sediments and
overlying water.
As far as I know, only a
handful of authors have even mentioned the importance of measuring
redox levels in sediments when it comes to sand beds in home
aquariums (e.g. Sam Gamble and Bob Goemans). Although the presence
of iron sulfide and oxides of iron in carbonate-dominated
sediments may not be that great (?) it nevertheless raises some
tempting comparisons to home aquariums. Certainly it brings
attention to the importance of avoiding anoxic conditions in
sediments, with its corresponding drop in redox. Perhaps this is
why some aquarists report algal blooms after several years of sand
bed usage or why some report algal problems with plenum systems
after a year or so? These systems may have developed greater
reducing environments (anoxic), resulting in the dissolution of P
rich compounds, which have previously been sequestered in the
sediments. Furthermore, using iron rich supplements may contribute
to a pool of iron sulfides accumulating in these anoxic areas over
time, again eventually resulting in an increase in soluble P
release to pore and surface waters.
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Anthony,
K.R.N., Connolly, S.R. and B.L. Willis. 2002. Comparative
analysis of energy allocation to tissue and skeletal
growth in corals. Limnology and Oceanography
47(5): 1417-1429.
Most studies
on coral growth look primarily at linear increases in
the skeleton and these rates are then used to judge
the effects of environmental stressors on coral growth
as an indication of health. However, very little work
has been done on how tissue growth reacts to changes
to environmental factors, and how this might relate to
an indication of coral health. In this paper the goal
was to develop a mathematical growth model to estimate
how much energy is allocated for coral tissue growth
and how much for skeletal growth, and then compare
this to experimental growth data gained from exposing
hemispherical (Goniastrea retiformis) and
branching colonies (Porites cylindrica) to
changes in environmental factors such as light (shaded
and unshaded) and physical stressors such as
sedimentation (filtered and raw seawater, low and high
levels of sediment). The model predicted that tissue
and skeletal growth would vary slightly from each
other when affected by environmental changes; however,
the results did not support their hypothesis. It was
found that investment in tissue growth varied fourfold
to tenfold more over a given environmental range (i.e.
light level, sediment level) than did investment into
skeletal growth in small colonies(2-3 cm radius) and branches, a much greater
variation than was predicted by the model. This was
primarily due to the fact that there was a wide range
in tissue growth responses that did not behave in a
linear fashion in relation to linear extension of the
skeleton. Due to this variation in tissue growth, they
proposed that skeletal growth rates are relatively
unaffected by the physical and environmental stressors
they used, with tissue either thickening or thinning
depending on the remaining resources available for
growth. Under stressful conditions (low light, high
sedimentation) energy available for tissue growth is
too limited for tissue growth to keep up with skeletal
growth, and the tissue begins to utilize its lipid
reserves. Given these results they concluded that
under stressful conditions, tissue growth is more
likely to be affected than skeletal growth, depending
on how much tissue mass there is and its quality (i.e.
lipid content): light and sediment load have a much
greater affect on tissue growth than on skeletal
growth. In other words, tissue growth responds more
strongly to resource availability and stressors than
skeletal growth does.
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For
aquarists this study has some practical implications. Many of us use
skeletal growth as a benchmark for how well our corals are doing. If
this study is correct, then simply using colony growth as a sign that
all is well may not be valid in every case. The thickness and quality of
the tissue may be of greater significance than how fast the skeleton
grows. It is thought that heterotrophy on the part of the coral can be a
mechanism whereby a coral can allocate enough energy to tissue growth to
allow it to keep up with skeletal growth. In fact, Anthony et al.
found that the corals in high (Goniastrea) and intermediate (Porites)
sediment loads actually showed increases in tissue growth, presumably
due to the ingestion of particles which supplied the corals with organic
carbon and other essential nutrients. This then argues against keeping
crystal clear tanks in my mind, and further illustrates the importance
of feeding or providing the necessary nutrients in other forms (i.e.
dissolved organic and inorganic nitrogen). Simply maximizing coral
growth rates either by chemical means (high calcium and alkalinity
levels) or physical means (high light, high temperatures) may not be
prudent unless mechanisms are also available for maximizing tissue
growth rates as well.
Interesting
Citations from the Periodical Literature
The
following are citations for some of the articles that might also be of
interest to aquarists, which were published in the summer and fall of
2002.
Aquaculture
Hotos, G. N. 2002.
Selectivity of the rotifer Brachionus plicatilis fed mixtures of
algal species with various cell volumes and densities. Aquaculture
Research 33(12): 949-958.
Cephalopods
Domingues, P.M.,
Sykes, A. and J.P. Andrade. 2002. The use of Artemia sp. or
mysids as food source for hatchlings of the cuttlefish(Sepia officinalis); effects on growth and survival
throughout the life cycle. Aquaculture International 9(4): 310-332.
Walsh, L.S., Turk,
P.E., Forsythe, J.W. and P.G. Lee. 2002. Mariculture of the loliginid
squid Sepiateuthis lessoniana through seven successive
generations. Aquaculture 212(1-4): 245-262.
Coral Biology
Anta, C.,
Gonzalez, N., Rodriguez, J. and C. Jimenez. 2002. A secosterol form the
Indonesian octocoral Pachyclavularia violocea. Journal of
Natural Products 65(9): 1357-1359.
Biseswar, R.,
Moodley, G.K. and A.D. Naido. 2002. Note on an inversion of intertidal
zoanthid colonies by a chaetopterid polychaete at Park Rynie Beach,
Kwazulu-Natal, South Africa. South African Journal of Marine Science
24:371-374.
LaJeunessa, T.C.
2002. Diversity and community structure of the symbiotic dinoflagellates
from Caribbean reefs. Marine Biology 141(2): 387-400.
Paul, V.J., Biggs,
J. and M. Slattery. 2002. Co-occurrence of chemical and structural
defenses in the gorgonian corals of Guam. Marine Ecology Progressive
Series 239: 105-114.
Shi, Y.P.,
Rodriguez, A.D., Barnes, C.L., Sanchez, J.A., Raptis, R.G. and P. Brown.
2002. New terpenoid constituents from Eunicea pinta. Journal
of Natural Products 65(9): 1232-1241.
Verde, E.A. and
L.R. McCloskey. 2002. A comparative analysis of the photobiology of
zooxanthellae and zoochlorellae symbiotic with the temperate anemone Anthepleura
elegantissima (Brandt) II. Effects of light intensity. Marine
Biology 141(2): 225-240.
Ecology
Kayanne, H., Hairi,
S., Ide, Y. and F. Akimoto. 2002. Recovery of coral populations after
the 1998 bleaching on Shiraho Reef, in the southern Ryukus, NW. Pacific.
Marine Ecology Progressive Series 239: 93-104.
Kemp, M.J. and W.K.
Dodds. 2002. The influence of ammonium, nitrate and dissolved oxygen
concentration on uptake, nitrification and denitrification rates
associated with prairie stream substrata. Limnology and Oceanography
47(5): 1380-1393.
Rasherd, M.,
Badran, M.I., Richter, C. and M. Huetel. 2002. Effect of reef framework
and bottom sediment on nutrient enrichment in a coral reef of the Gulf
of Aqaba, Red Sea. Marine Ecology Progressive Series 239: 277-286.
Fish
Sakai, Y., Karino,
K., Nakashima, Y. and B. Kramer. 2002. Status-dependant behavioural sex
change in a polygynous coral-reef fish, Halichoeres melanurus. Journal
of Ethology 20(2): 101-106.
Whiteman, E.A. and
L.M. Cote. 2002. Sex differences in cleaning behaviour and diet of a
Caribbean cleaning goby. Journal of Marine Biological Association of
the UK 82(4): 655-664.
Marine Plants
Foururean, J.W.
and J.C. Zieman. 2002. Nutrient content of the seagrass Thalassia
testudinum reveals regional patterns of relative availability of
nitrogen and phosphorus in the Florida Keys, USA. Biogeochemisty
61(3): 229-246.
Sponges
Erickson, K.L.,
Gustafson, K.R., Pannell, L.K., Beutler, J.A. and M.R. Boyd. 2002. New
dimeric macrolide glycosides from the marine sponge Myriastra clavosa.
Journal of Natural Products 65(9): 1303-1306.
Liu, Y.H., Hong,
J.K., Lee, C.O., Im, K.S., Kim, N.P., Choi, J.S. and J.H. Jung. 2002.
Cytotoxic pyrrolo- and furano terpenoids from the sponge Sarcotragus sp.
Journal of Natural Products 65(9): 1307-1314.
Sandler, J.S.,
Colin, P.L., Hooper, J.N.A. and D.J. Faulkner. 2002. Cytotoxic β-carbolines
and cyclic peroxides from the palauan sponge Plakortis nigra. Journal
of Natural Products 65(9): 1258-1261.
Williams, P.G.,
Yoshida, W.Y., Moore, R.E. and V.J. Paul. 2002. Tasiamide, a cytotoxic
peptide from the marine cyanobacterium Symploca sp. Journal of
Natural Products 65(9): 1136-1339.
