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Published (Version of record)Attribution 2.0 Generic (CC BY 2.0), Open Access
Published (Version of record)Attribution 2.0 Generic (CC BY 2.0), Open
Journal article
Nitrogen enrichment and speciation in a coral reef lagoon driven by groundwater inputs of bird guano
Journal of geophysical research. Oceans, Vol.122(9), pp.7218-7236
09/2017
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Abstract
While the influence of river inputs on coral reef biogeochemistry has been investigated, there is limited information on nutrient fluxes related to submarine groundwater discharge (SGD). Here, we investigate whether significant saline groundwater‐derived nutrient inputs from bird guano drive coral reef photosynthesis and calcification off Heron Island (Great Barrier Reef, Australia). We used multiple experimental approaches including groundwater sampling, beach face transects, and detailed time series observations to assess the dynamics and speciation of groundwater nutrients as they travel across the island and discharge into the coral reef lagoon. Nitrogen speciation shifted from nitrate‐dominated groundwater (>90% of total dissolved nitrogen) to a coral reef lagoon dominated by dissolved organic nitrogen (DON; ∼86%). There was a minimum input of nitrate of 2.1 mmol m−2 d−1 into the lagoon from tidally driven submarine groundwater discharge estimated from a radon mass balance model. An independent approach based on the enrichment of dissolved nutrients during isolation at low tide implied nitrate fluxes of 5.4 mmol m−2 d−1. A correlation was observed between nitrate and daytime net ecosystem production and calcification. We suggest that groundwater nutrients derived from bird guano may offer a significant addition to oligotrophic coral reef lagoons and fuel ecosystem productivity and the coastal carbon cycle near Heron Island. The large input of groundwater nutrients in Heron Island may serve as a natural ecological analogue to other coral reefs subject to large nutrient inputs from anthropogenic sources.
Key Points
We reveal significant saline groundwater‐derived nutrient inputs from bird guano into a coral reef lagoon in the Great Barrier Reef
Nitrogen speciation shifted from nitrate‐dominated groundwater to a coral reef lagoon dominated by dissolved organic nitrogen
The large input of nutrients may serve as a natural analogue to coral reefs subject to large nutrient inputs from anthropogenic sources
Details
- Title
- Nitrogen enrichment and speciation in a coral reef lagoon driven by groundwater inputs of bird guano
- Creators
- Ashly McMahon - Southern Cross UniversityIsaac R Santos - Southern Cross University
- Publication Details
- Journal of geophysical research. Oceans, Vol.122(9), pp.7218-7236
- Publisher
- Amer Geophysical Union
- Number of pages
- 19
- Grant note
- Australian Research Council (DP120101645; DE140101733; DP110103638)
- Identifiers
- 991012926961902368
- Academic Unit
- National Marine Science Centre; Faculty of Science and Engineering
- Language
- English
- Resource Type
- Journal article