Macroalgae reveal nitrogen enrichment and elevated N:P ratios on the Belize Barrier Reef. (October 2021)

• Record Type: Journal Article
• Authors: Lapointe, Brian E.; Tewfik, Alexander; Phillips, Myles
• Is Part Of: Marine pollution bulletin. Volume 171(2021)
• Publication Date: 2021-10
• Subjects: Eutrophication -- Coral reefs -- Macroalgae -- Nitrogen -- Phosphorus -- Stable isotopes; Marine pollution -- Periodicals; Marine Biology -- Periodicals; Water Pollution -- Periodicals; Mer -- Pollution -- Périodiques; Publications périodiques; Pollution des mers; Lutte antipollution; Electronic journals; 363.7394
• DOI: 10.1016/j.marpolbul.2021.112686
• Languages: English
• ISSNs: 0025-326X

Abstract

Abstract: Macroalgal blooms are increasing on the Belize Barrier Reef (BBR) as scleractinian coral cover declines. Although some have attributed this to reduced grazing, the role of land-based nutrient pollution has not been assessed. Nutrient enrichment was quantified through macroalgal tissue analysis from Belize City to the offshore fore reef and at several central BBR lagoon sites. These recent data were compared to baseline data from the 1980s. Significant nearshore-to-offshore gradients of %N, %P and δ 13 C in macroalgae all indicated land-based sources of these nutrients. Macroalgal δ 15 N values were generally enriched in nearshore waters where values matched those reported for human sewage. Notably, the N:P ratios of recent macroalgae measurements were elevated at all sites, more than two-fold higher than values from the 1980s (~30: 1 to 70:1). These results support the hypothesis that nitrogen enrichment from land-based sources has increased phosphorus limitation driving macroalgal blooms and coral stress on the BBR. Highlights: Role of land-based nutrient pollution has not been assessed on the Belize Barrier Reef. Nutrient enrichment was quantified through macroalgal tissue analysis. Recent data was compared to baseline data from the 1980s. Stable isotopes and elemental ratios indicated land-based sources of nutrients. Increasing land-based nutrient pollution has driven macroalgal blooms and coral stress.