title: Differences in urbanization and degree of marine influence are reflected in delta13C and delta15N of producers and consumers in seagrass habitats of Puerto Rico.
abstract: 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 delta(13)C and delta(15)N in producers and consumers. delta(15)N values were influenced by human activity: the food web from sites near urbanized centers was on average 1 per thousand heavier in delta(15)N compared to undeveloped sites. This is most likely due to wastewater inputs from septic systems relatively near the shoreline. Changes in delta(13)C were best explained by differences in the degree of marine influence. Where terrestrial inputs from a major river dominated, delta(13)C values were lighter, whereas sites further from land and in locations exposed to oceanic currents had heavier delta(13)C 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 to precipitation.
authors.affiliation: The Ecosystems Center, Marine Biological Laboratory, 7 MBL St., Woods Hole, MA 02543, USA. yolsen@bangor.ac.uk
authors.forename: Ylva S
authors.initials: YS
authors.lastname: Olsen
authors.forename: Sophia E
authors.initials: SE
authors.lastname: Fox
authors.forename: Erin L
authors.initials: EL
authors.lastname: Kinney
authors.forename: Mirta
authors.initials: M
authors.lastname: Teichberg
authors.forename: Ivan
authors.initials: I
authors.lastname: Valiela
mesh_terms: D002247:Carbon Isotopes / Q000032:analysis; D017753:Ecosystem; D020387:Food Chain; D031321:Hydrocharitaceae / Q000737:chemistry; D009587:Nitrogen Isotopes / Q000032:analysis; D011647:Puerto Rico; D012623:Seawater / Q000032:analysis*; D012722:Sewage / Q000737:chemistry; D012987:Soil / Q000032:analysis*; D014507:Urbanization
chemical_list: D002247:Carbon Isotopes; D009587:Nitrogen Isotopes; D012722:Sewage; D012987:Soil