Olsen, Ylva S., Sophia E. Fox, Erin L. Kinney, Mirta Teichberg, and Ivan Valiela. 2010. Differences in urbanization and degree of marine influence are reflected in delta(13)C and delta(15)N of producers and consumers in seagrass habitats of puerto rico. Marine Environmental Research 69 (3) (APR): 198-206.
Couplings between land use and marine food webs in tropical systems are poorly understood. We compared
land–sea coupling in seven sites around Puerto Rico, differing in the degree of precipitation and
urbanization, by measuring d13C and d15N in producers and consumers. d15N values were influenced by
human activity: the food web from sites near urbanized centers was on average 1‰ heavier in d15N compared
to undeveloped sites. This is most likely due to wastewater inputs from septic systems relatively
near the shoreline. Changes in d13C were best explained by differences in the degree of marine influence.
Where terrestrial inputs from a major river dominated, d13C values were lighter, whereas sites further
from land and in locations exposed to oceanic currents had heavier d13C values, characteristic of a marine
source of dissolved organic carbon. We found no significant effect of precipitation on connectivity in spite
of a twofold difference in annual average rainfall between the north and south coast. The results suggest
there is some connectivity between land and sea in Puerto Rico, despite high rates of evaporation relative