Dataset Information

Coral Skeleton ?15N as a Tracer of Historic Nutrient Loading to a Coral Reef in Maui, Hawaii.

ABSTRACT: Excess nutrient loading to nearshore environments has been linked to declining water quality and ecosystem health. Macro-algal blooms, eutrophication, and reduction in coral cover have been observed in West Maui, Hawaii, and linked to nutrient inputs from coastal submarine groundwater seeps. Here, we present a forty-year record of nitrogen isotopes (?15N) of intra-crystalline coral skeletal organic matter in three coral cores collected at this site and evaluate the record in terms of changes in nitrogen sources. Our results show a dramatic increase in coral ?15N values after 1995, corresponding with the implementation of biological nutrient removal at the nearby Lahaina Wastewater Reclamation Facility (LWRF). High ?15N values are known to be strongly indicative of denitrification and sewage effluent, corroborating a previously suggested link between local wastewater injection and degradation of the reef environment. This record demonstrates the power of coral skeletal ?15N as a tool for evaluating nutrient dynamics within coral reef environments.

SUBMITTER: Murray J

PROVIDER: S-EPMC6447536 | biostudies-literature | 2019 Apr

REPOSITORIES: biostudies-literature

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Coral Skeleton δ<sup>15</sup>N as a Tracer of Historic Nutrient Loading to a Coral Reef in Maui, Hawaii.

Murray Joseph J Prouty Nancy G NG Peek Sara S Paytan Adina A

Scientific reports 20190403 1

Excess nutrient loading to nearshore environments has been linked to declining water quality and ecosystem health. Macro-algal blooms, eutrophication, and reduction in coral cover have been observed in West Maui, Hawaii, and linked to nutrient inputs from coastal submarine groundwater seeps. Here, we present a forty-year record of nitrogen isotopes (δ<sup>15</sup>N) of intra-crystalline coral skeletal organic matter in three coral cores collected at this site and evaluate the record in terms of ...[more]

PMID: 30944391

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Project description:Both natural and anthropogenic stressors are increasing on coral reefs, resulting in large-scale loss of coral and potential shifts from coral- to macroalgae-dominated community states. Two factors implicated in shifts to macroalgae are nutrient enrichment and fishing of reef herbivores. Although either of these factors alone could facilitate establishment of macroalgae, reefs may be particularly vulnerable to coral-to-algae phase shifts in which strong bottom-up forcing from nutrient enrichment is accompanied by a weakening of herbivore control of macroalgae via intense fishing. We explored spatial heterogeneity and covariance in these drivers on reefs in the lagoons of Moorea, French Polynesia, where the local fishery heavily targets herbivorous fishes and there are spatially variable inputs of nutrients from agricultural fertilizers and wastewater systems. Spatial patterns of fishing and nutrient enrichment were not correlated at the two landscape scales we examined: among the 11 interconnected lagoons around the island or among major habitats (fringing reef, mid-lagoon, back reef) within a lagoon. This decoupling at the landscape scale resulted from patterns of covariation between enrichment and fishing that differed qualitatively between cross-shore and long-shore directions. At the cross-shore scale, nutrient enrichment declined but fishing increased from shore to the crest of the barrier reef. By contrast, nutrient enrichment and fishing were positively correlated in the long-shore direction, with both increasing with proximity to a pass in the barrier reef. Contrary to widespread assumptions in the scientific literature that human coastal population density correlates with impact on marine ecosystems and that fishing effort declines linearly with distance from the shore, these local stressors produced a complex spatial mosaic of reef vulnerabilities. Our findings support spatially explicit management involving the control of anthropogenic nutrients and strategic reductions in fishing pressure on herbivores by highlighting specific areas to target for management actions.

Dataset Information

Coral Skeleton ?15N as a Tracer of Historic Nutrient Loading to a Coral Reef in Maui, Hawaii.

Publications

Coral Skeleton δ<sup>15</sup>N as a Tracer of Historic Nutrient Loading to a Coral Reef in Maui, Hawaii.

Similar Datasets

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