Macroalgal responses to experimental nutrient enrichment in shallow coastal waters : growth, internal nutrient pools, and isotopic signatures
Fox, Sophia E.
Olsen, Ylva S.
MetadataShow full item record
KeywordMacroalgal blooms; Eutrophication; Nutrient limitation; N uptake; Assimilation; Ulva spp.; Gracilaria spp.; Nitrate; Ammonium; Phosphate
Increased nutrient inputs to temperate coastal waters have led to increased occurrences of macroalgal blooms worldwide. To identify nutrients that are limiting to macroalgae and to determine whether different forms of these nutrients and long-term ambient nutrient conditions affect macroalgal response, we used in situ enrichment methods and tested the response of 2 bloom-forming species of macroalgae, Ulva lactuca and Gracilaria tikvahiae, from shallow estuaries of Waquoit Bay, Massachusetts, USA, that receive different land-derived N inputs. We enriched caged macroalgal fronds with nitrate, ammonium, phosphate, and N + P combinations, and measured growth, nutrient content, and δ15N signatures of fronds after 2 wk of incubation. In these estuaries, P did not limit growth, however, the 2 species differed in growth response to N additions. Growth of U. lactuca was greater in Childs River (CR), the estuary with higher nitrate inputs, than in Sage Lot Pond (SLP); growth in SLP increased with nitrate and ammonium enrichment. In contrast, growth of G. tikvahiae was greater in SLP than in CR, but had no growth response to N enrichment in either site. C and N contents differed initially between species and sites, and after nutrient enrichment. Final tissue % N increased and C:N decreased after nitrate and ammonium enrichment. δ15N values of the macroalgae demonstrated uptake of the experimental fertilizers, and a higher affinity and faster turnover of internal N pools with ammonium than nitrate enrichment in both species. We suggest that U. lactuca blooms in areas with both high nitrate and ammonium water column concentrations, and is more N-limited in oligotrophic waters where DIN levels are too low to sustain high growth rates. G. tikvahiae has a greater N storage capacity than U. lactuca, which may allow it to grow in less nutrient-rich waters.
Author Posting. © Inter-Research, 2008. This article is posted here by permission of Inter-Research for personal use, not for redistribution. The definitive version was published in Marine Ecology Progress Series 368 (2008): 117-126, doi:10.3354/meps07564.
Showing items related by title, author, creator and subject.
Farm management, not soil microbial diversity, controls nutrient loss from smallholder tropical agriculture Wood, Stephen A.; Almaraz, Maya; Bradford, Mark A.; McGuire, Krista L.; Naeem, Shahid; Neill, Christopher; Palm, Cheryl A.; Tully, Katherine L.; Zhou, Jizhong (Frontiers Media, 2015-03-04)Tropical smallholder agriculture is undergoing rapid transformation in nutrient cycling pathways as international development efforts strongly promote greater use of mineral fertilizers to increase crop yields. These changes ...
DeCarlo, Thomas M.; Cohen, Anne L.; Barkley, Hannah C.; Cobban, Quinn; Young, Charles W.; Shamberger, Kathryn E. F.; Brainard, Russell E.; Golbuu, Yimnang (2014-10)Coral reefs exist in a delicate balance between calcium carbonate (CaCO3) production and CaCO3 loss. Ocean acidification (OA), the CO2-driven decline in seawater pH and CaCO3 saturation state (Ω), threatens to tip this ...
Rintoul, Stephen R. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1988-03)Inverse methods are applied to historical hydrographic data to address two aspects of the general circulation of the Atlantic Ocean. The method allows conservation statements for mass and other properties, along with a ...