1987 
Kieber, D. J. (1988) Marine biogeochemistry of alpha-keto acids. Ph. D. Dissertation. 
University of Miami, Coral Gables, FL. 243 pp. 
There is an increasing awareness of the importance of dissolved organic matter (DOM) 
in a variety of physical, chemical, and biological processes in seawater. Measurements 
of specific components of DOM (e.g., amino acids) have provided valuable insights into 
these processes. a-Keto acids represent a potentially important component of DOM; 
however, their marine biogeochemistry is poorly understood. Therefore, a detailed 
investigation of processes affecting cycling of a-keto acids in seawater was 
undertaken. Initial studies demonstrated that a-keto acids were formed when filtered 
seawater was irradiated with sunlight. Average photochemical production rates for 
Biscayne Bay seawater were 8.2 and 5.7 nM W' 1 hr' 1 nr 2 for glyoxylic and pyruvic 
acids respectively. Photochemical production rates varied significantly for seawater 
collected from distinctly different regions of the sea. Higher production rates were 
observed for seawater from coastal locations (e.g., Biscayne Bay, Florida Bay) 
relative to oligotrophic seawater from the Sargasso Sea or the Gulf Stream. 
Photochemical decarboxylation rates of a-keto acids were determined using 
radiolabeled tracers. Decarboxylation rates were less than 5% of photoproduction 
rates. Slow rates of decarboxylation indicated that the major removal pathway of a- 
keto acids in seawater was biological and not chemical. Midday photochemical 
production rates of a-keto acids were highly correlated with their rate of biological 
uptake (pyruvate, r = 0.967; glyoxylate, r = 0.736) suggesting that these processes 
may be closely related in the photic zone. These results suggest that photochemical 
processes may play an important role in the transformation and remineralization of 
DOM in the photic zone. An intensive field study was undertaken to assess the spatial 
and temporal distribution of a-keto acids in the northwest Atlantic Ocean and Cariaco 
Trench. Physical, chemical, and biological factors were important determinants 
controlling the cycling of these compounds in the sea. Oxic-anoxic interfaces or the 
onset of a sharp pycnocline were particularly active zones of a-keto acid production 
and consumption. Strong diurnal fluctuations in a-keto concentrations were often 
observed in surface seawater. A potentially important degradation pathway of 
biologically refractory dissolved organic carbon (DOC) is its photochemical oxidation in 
the photic zone. a-Keto acids were not quantitatively important oxidation products of 
this process; their production represented less than 0.1% of DOC oxidized. 
1987 0 
Livingston, R. J. (1987) Historic trends of human impacts on seagrass meadows in Florida. 
Fla. Mar. Res. PubL 42:139-151. 
[DATE OF SAMPLING UNKNOWN OR NOT APPLICABLE.] Since 1940, Florida has 
undergone unprecedented population growth, which is expected to accelerate into the 
next century. Municipalization, industrialization, and agricultural activities in coastal 
drainage systems have been accompanied by various impacts in almost every bay 
system in Florida. Seagrass meadows have been virtually eliminated in most portions of 
the Pensacola Bay and Tampa Bay systems. Significant losses have been noted over the 
past 20 - 40 yrs in Choctawhatchee Bay, Apalachee Bay, Charlotte Harbor, Biscayne 
Bay, and the Indian River. A lack of reliable data precludes appropriate evaluations in 
other areas. However, the two primary concentrations of seagrasses in the northern 
hemisphere, Florida Bay and the northwest Gulf coast (including Apalachee Bay), are 
currently threatened by wide-ranging forms of human activity, which include 
freshwater diversion, agricultural activities, dredging, and offshore oil drilling The 
general lack of long-term, multidisciplinary ecological studies has inhibited a thorough 
understanding of the problem. Recent studies in Apalachee Bay indicate that relatively 
minor water-quality changes can destroy or severely alter seagrass distribution and 
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