Controls on the nitrogen isotopic composition of shallow water corals across a tropical reef flat transect

Erler, Dirk V.; Wang, Xingchen; Sigman, Daniel M.; Scheffers, Sander; Shepherd, Benjamin

doi:10.1007/s00338-014-1215-5

Cited by 31 publications

(23 citation statements)

References 53 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Two δ 15 N marine values (1‰, 5‰) were used to span the reported range from values for “new” N entering the surface ocean (low end‐member) to surface ocean δ 15 N‐TDN values (high end‐member) (Knapp et al , ; Ryabenko et al ; Thibodeau et al ). This δ 15 N range corresponds with those for algae in Moreton Bay at the BRE mouth (0–7‰) (Costanzo et al ) and for Coral Sea TDN and NO 3 − (2–5‰) (Erler et al ; Yoshikawa et al ). The f was calculated from salinity (Eq.…”

Section: Methodssupporting

confidence: 78%

δ¹⁵N patterns in three subtropical estuaries show switch from nitrogen “reactors” to “pipes” with increasing degradation

Hipsey

Eyre

2018

Limnology & Oceanography

View full text Add to dashboard Cite

Ongoing alterations to estuaries by inland agricultural intensification and coastal development could affect their capacity to regulate the flux of excess terrestrial nitrogen (N) to the coastal ocean. Here, a new multiform δ 15 N metric was developed to measure how "pristine," moderately impacted, and highly degraded estuaries recycle (assimilation, mineralization) and remove (denitrification, anaerobic ammonium oxidation) N. Organic (dissolved and particulate, δ 15 N and δ 13 C) and inorganic (nitrate and ammonium, δ 15 N and δ 18 O) N forms were measured over the salinity gradient in the wet and dry season in subtropical estuaries receiving increasing terrestrial N loads (pristine: 16 kg N d −1 , moderate: 150 kg N d −1 , degraded: 630 kg N d −1 ). The difference in the inorganic vs. organic pool δ 15 N composition increased between the pristine (0 AE 2‰), moderate (10 AE 6‰), and degraded (20 AE 8‰) systems, indicating that N recycling decreased as degradation increased. The N 2 O concentrations, NO 3 − dual isotope values, and offsets between "measured" and "mixing expected" δ 15 N values further revealed that microbial processes removed up to 30% of the N load entering the moderately degraded estuary, but only 9% in the highly degraded estuary. Hydrologic differences (depth and flushing times [FTs]) could not fully explain these shifts in N fate between the estuaries and seasons, which instead aligned with nonlinear increases in phytoplankton biomass and light penetration with increasing N loads. These isotopic indicators provide direct evidence that estuaries switch from "reactors" that assimilate and remove terrestrial N to "pipes" that transport N directly to sea as degradation increases.

show abstract

Section: Methodssupporting

confidence: 78%

δ¹⁵N patterns in three subtropical estuaries show switch from nitrogen “reactors” to “pipes” with increasing degradation

Hipsey

Eyre

2018

Limnology & Oceanography

View full text Add to dashboard Cite

show abstract

“…The new method for CS-δ 15 N analysis is adequately precise (1 σ = 0.2‰) to capture even modest changes in CS-δ 15 N (Wang et al, 2015). Further, it has already been shown that CS-δ 15 N measured in this way can be used to trace small (~1‰) spatial fluctuations in external water column δ 15 N (Erler et al, 2015). The natural progression in the development of this new proxy is the reconstruction of long-term (> 100 yr) temporal CS-δ 15 N records at semiannual/annual resolution.…”

Section: Introductionmentioning

confidence: 94%

“…Food-web structure in a marine ecosystem therefore affects the δ 15 N of the different components of that ecosystem (Michener and Kaufman, 2007), some of which are accessed during feeding by corals. Moreover, and separate from any δ 15 N change in a given prey item, both physiological and trophic changes in zooxanthellate corals can alter their tissue δ 15 N (Erler et al, 2015;Reynaud et al, 2009;Wang et al, 2015). Anthropogenic N enrichment therefore works to alter CS-δ 15 N in multiple ways, including: (1) changes in the δ 15 N of the source of inorganic and particulate N to a system; (2) changes in the δ 15 N of N available to the coral through shifting food-web structure; and (3) changes in the internal cycling of N between coral and symbiont as a result of coral feeding rate and/or zooxanthellae growth rate (Table 1).…”

Section: Introductionmentioning

confidence: 99%

Nitrogen isotopic composition of organic matter from a 168 year-old coral skeleton: Implications for coastal nutrient cycling in the Great Barrier Reef Lagoon

Erler

Wang

Sigman

et al. 2016

Earth and Planetary Science Letters

Self Cite

View full text Add to dashboard Cite

Ongoing human activities are known to affect nitrogen cycling on coral reefs, but the full history of anthropogenic impact is unclear due to a lack of continuous records. We have used the nitrogen isotopic composition of skeleton-bound organic matter (CS-δ 15 N) in a coastal Porites coral from Magnetic Island in the Great Barrier Reef as a proxy for N cycle changes over a 168 year period (1820-1987 AD). The Magnetic Island inshore reef environment is considered to be relatively degraded by terrestrial runoff; given prior CS-δ 15 N studies from other regions, there was an expectation of both secular change and oscillations in CS-δ 15 N since European settlement of the mainland in the mid 1800's. Surprisingly, CSδ 15 N varied by less than 1.5‰ despite significant land use change on the adjacent mainland over the 168-year measurement period. After 1930, CS-δ 15 N may have responded to changes in local river runoff, but the effect was weak. We propose that natural buffering against riverine nitrogen load in this region between 1820 and 1987 is responsible for the observed stability in CS-δ 15 N. In addition to coral derived skeletal δ 15 N, we also report, for the first time, δ 15 N measurements of non-coral derived organic N occluded within the coral skeleton, which appear to record significant changes in the nature of terrestrial N inputs. In the context of previous CS-δ 15 N records, most of which yield CS-δ 15 N changes of at least 5‰, the Magnetic Island coral suggests that the inherent down-core variability of the CS-δ 15 N proxy is less than 2‰ for Porites.

show abstract

“…Water samples from the 2018/2019 Burdekin River flood plume, collected by AIMS staff, and water samples from Sites 4 to 6 (November 2018), were collected from 1 and 5 m depth at each site using a Niskin water sampler. All water samples were analysed for total dissolved nitrogen concentration (flow injection analysis), and the δ 15 N of total dissolved nitrogen 63,64 . The δ 15 N and N content of particulate N trapped on pre-combusted glass fibre filter paper was determined on samples (8-24 L) collected from Sites 4 to 6 (November 2018).…”

Section: Resultsmentioning

confidence: 99%

Coral skeletons reveal the history of nitrogen cycling in the coastal Great Barrier Reef

et al. 2020

Self Cite

View full text Add to dashboard Cite

Anthropogenic nutrient discharge to coastal marine environments is commonly associated with excessive algal growth and ecosystem degradation. However in the world's largest coral reef ecosystem, the Great Barrier Reef (GBR), the response to enhanced terrestrial nutrient inputs since European settlement in the 1850's remains unclear. Here we use a 333 year old composite record (1680-2012) of 15 N/ 14 N in coral skeleton-bound organic matter to understand how nitrogen cycling in the coastal GBR has responded to increased anthropogenic nutrient inputs. Our major robust finding is that the coral record shows a long-term decline in skeletal 15 N/ 14 N towards the present. We argue that this decline is evidence for increased coastal nitrogen fixation rather than a direct reflection of anthropogenic nitrogen inputs. Reducing phosphorus discharge and availability would short-circuit the nitrogen fixation feedback loop and help avoid future acute and chronic eutrophication in the coastal GBR.

show abstract

Controls on the nitrogen isotopic composition of shallow water corals across a tropical reef flat transect

Cited by 31 publications

References 53 publications

δ¹⁵N patterns in three subtropical estuaries show switch from nitrogen “reactors” to “pipes” with increasing degradation

δ¹⁵N patterns in three subtropical estuaries show switch from nitrogen “reactors” to “pipes” with increasing degradation

Nitrogen isotopic composition of organic matter from a 168 year-old coral skeleton: Implications for coastal nutrient cycling in the Great Barrier Reef Lagoon

Coral skeletons reveal the history of nitrogen cycling in the coastal Great Barrier Reef

Contact Info

Product

Resources

About

Controls on the nitrogen isotopic composition of shallow water corals across a tropical reef flat transect

Cited by 31 publications

References 53 publications

δ15N patterns in three subtropical estuaries show switch from nitrogen “reactors” to “pipes” with increasing degradation

δ15N patterns in three subtropical estuaries show switch from nitrogen “reactors” to “pipes” with increasing degradation

Nitrogen isotopic composition of organic matter from a 168 year-old coral skeleton: Implications for coastal nutrient cycling in the Great Barrier Reef Lagoon

Coral skeletons reveal the history of nitrogen cycling in the coastal Great Barrier Reef

Contact Info

Product

Resources

About

δ¹⁵N patterns in three subtropical estuaries show switch from nitrogen “reactors” to “pipes” with increasing degradation

δ¹⁵N patterns in three subtropical estuaries show switch from nitrogen “reactors” to “pipes” with increasing degradation