Nitrogen fixation by Trichodesmium spp. in the Central and Northern Great Barrier Reef Lagoon:relative importance of the fixed-nitrogen load

Bell, P. R. F.; Elmetri, Ibrahim; Uwins, Philippa J.R.

doi:10.3354/meps186119

Cited by 67 publications

(72 citation statements)

References 11 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The latter have been identified as nutrient increases during the 3-7 preceding days for all 425 the blooms, which supports observations made by Carpenter and Price (1977), Bell et al (1999), 426 seem to be the best candidates, although such a statement cannot be proved for a lack of 437 measurements. 438 increases are very quick responses to NO 3 inputs.…”

Section: Causes Of Bloom Developments: Favorable Conditions and Triggsupporting

confidence: 69%

Population dynamics and environmental conditions affecting Trichodesmium spp. (filamentous cyanobacteria) blooms in the south–west lagoon of New Caledonia

Rodier

Borgne²

2008

Journal of Experimental Marine Biology and Ecology

View full text Add to dashboard Cite

Abstract. The present description of Trichodesmium spp. population dynamics and associated 1 environmental variables is the first one using a very short sampling interval (2-3 days). Such a 2 strategy allows a fine description of changes involving the population density and characteristics. It 3 also lends itself to interpreting those changes from past environmental conditions. During the two 4 surveys, 2 and 5 month-long, T. erythraeum dominated the Trichodesmium population, with 5 temporary occurrence of T. thiebautii and five blooms could be described. These events appeared at 6 temperatures > 24°C and followed, in all cases, nitrate, soluble reactive phosphorus and chlorophyll 7 a enrichments, with a 3-7 day time lag. Low wind speed (< 4m s -1 ) was not a prerequisite for 8Trichodesmium bloom developments as long as temperatures exceeded 26°C. As abundance 9 increased during the bloom, so did the number of filaments (trichomes) in colonies and their 10 buoyancy, leading to a clear positive biomass gradient from the bottom to the surface. A simple 11 model, using variable growth rates, showed trichome ascent would be responsible for 87-99% of 12 concentrations at 0.5m, with Trichodesmium net growth rates ranging from 0.11 to 0.38 d -1 . Finally, 13 rapid trichome density declines could be ascribed to nutrient depletion and massive surface death 14 following ascent. 15 16 17

show abstract

Section: Causes Of Bloom Developments: Favorable Conditions and Triggsupporting

confidence: 69%

Population dynamics and environmental conditions affecting Trichodesmium spp. (filamentous cyanobacteria) blooms in the south–west lagoon of New Caledonia

Rodier

Borgne²

2008

Journal of Experimental Marine Biology and Ecology

View full text Add to dashboard Cite

show abstract

“…Method 3 assumed that all cellular nitrogen was due to N-fixation and determined the amount of new-N required to establish a surface aggregation of Trichodesmium. Bell et al (1999) study found that the annual Trichodesmium N-input for the Northern GBR ranged between 900-3700 t y -1 compared with measured river N-inputs of about 10,000 t y. Similarly for the Central GBR estimates of annual Trichodesmium N-input ranged from 12,000-30,000 t y -1 compared with river N-inputs of about 20,000 t y -1 (Bell et al 1999).…”

mentioning

confidence: 99%

“…Trichodesmium is considered an important source of new-nitrogen to the world's oceans (Mulholland 2007). Within the GBR, it is estimated that the annual N-input associated with Trichodesmium N-fixation is at least similar in magnitude to that from river inputs (Bell et al 1999;Furnas et al 1995). Bell et al (1999) calculated Trichodesmium N-fixation rates for the GBR using three different methods.…”

mentioning

confidence: 99%

“…Within the GBR, it is estimated that the annual N-input associated with Trichodesmium N-fixation is at least similar in magnitude to that from river inputs (Bell et al 1999;Furnas et al 1995). Bell et al (1999) calculated Trichodesmium N-fixation rates for the GBR using three different methods. Method 1 estimated N-fixation based upon the average annual distribution of Trichodesmium, whereas Method 2 considered the average concentration and duration of Trichodesmium surface aggregation events.…”

mentioning

confidence: 99%

See 1 more Smart Citation

A simple, binary classification algorithm for the detection of Trichodesmium spp. within the Great Barrier Reef using MODIS imagery

McKinna

Furnas

Ridd

2011

Limnology & Ocean Methods

View full text Add to dashboard Cite

A binary classification algorithm to detect the presence of high surface concentrations of the nitrogen‐fixing cyanobacterium Trichodesmium spp. was developed for high spatial resolution (250 m) imagery of the Moderate‐resolution Imaging Spectroradiometer (MODIS). Above‐water hyperspectral radiometric measurements of dense Trichodesmium surface aggregations (>10 µg/L Chlorophyll a) showed that the water‐leaving radiance Lw at wavelengths greater than 700 nm were much higher in magnitude (>0.05 W m−2sr−1) relative to the visible wavelengths 400–700 nm (<0.03 W m−2sr−1). The binary classification algorithm is based on three criteria. The first criteria relied on the difference in magnitude between the MODIS normalized water‐leaving radiance (nLw) at the 859 and 678 nm wavebands. The magnitude of the nLw at the 555 and 645 nm wavebands relative to nLw 678 nm waveband formed the second and third criteria, respectively. The classification algorithm was tested on a small subset of 13 MODIS images with corresponding Trichodesmium sea‐truths and yielded an 85% accuracy. Fine‐scale features consistent with dense Trichodesmium surface aggregations, such as eddy swirls and windrows, appear to be well represented with the algorithm results. The algorithm was also found to be robust in the presence of highly reflective, potential confounding effects.

show abstract

“…This observation ignores the work that suggests that Trichodesmium populations have increased significantly in the Low Isles region and that Trichodesmium growth is far more prolific in the P-PO 4 rich GBR regions (Bell and Elmetri 1995;Bell et al 1999).…”

mentioning

confidence: 91%

Response to “Selective Evidence of Eutrophication in the Great Barrier Reef” by Furnas et al.

Bell

Elmetri²,

Lapointe

2014

AMBIO

View full text Add to dashboard Cite

. Furnas et al. (2014) suggest that our conclusions are based upon limited sampling programs. However, we note that our principal conclusions, namely, (i) that hard coral cover in the Great Barrier Reef (GBR) has reduced by [70 % over the past century and (ii) that most GBR regions are characterized by Chl a values exceeding the defined chronic-eutrophic state (i.e., [0.2 mg m -3 ), are based on the extensive AIMS assembled data sets (e.g., see Fig. 3 in Bell et al. 2014).Furnas et al. note that the ocean color data presented in Figs. 4 and 5, and in particular the data in the near-shore regions, do not represent accurate levels of Chl a. We generally agree with this assessment but note that we have not used these data in deriving the Eutrophication Threshold Model (ETM). We note that offshore CZCS data sets were calibrated against field data from the late 1970s and early 1980s, and these calibrated data sets were used to demonstrate that elevated Chl a values occurred in the central and outer GBR lagoon and in remote GBR regions (e.g., see Bell and Gabric 1990;Gabric et al. 1990). The CZCS data also show that elevated phytoplankton productivity occurs ''downstream'' of reef complexes; this information can be used to assess the importance of N-fixation. Figures 4 and 5 are given in the Review paper (Bell et al. 2014) to illustrate these points and to show that more than three decades ago enough information was available for one to recognize the synoptic-scale chroniceutrophic state of the GBR; this information was largely ignored by the marine-science community.Furnas et al. note that some GBR regions characterized by annual mean Chl a[0.3 mg m -3 have healthy reefs and hence the setting of the trigger-value range of 0.40-0.45 mg m -3 . However, we note that many unhealthy reefs exist in regions where the annual mean Chl a is \0.3 mg m -3 . For example, the Lizard Is region has an annual mean Chl a value of *0.25 mg m -3 but has a median coral cover of 10-20%; far below that expected for a healthy reef (AIMS 2012). We note that various factors need to be considered when defining trigger values. In particular, the observation that COTS larvae and coral skeletal diseases (CSDs) will probably proliferate in waters characterized by Chl a\0.3 mg m -3 suggests that lower trigger values need to be set. We note that the recommended Chl a values for the outer Florida Keys lie essentially within the lower ETC-Chl a range i.e., 0.2-0.3 mg m -3 (McGee 2010).Furnas et al. state there is no evidence of increases in the fertility of the GBR lagoon. This comment ignores the results from the Low Isles studies which suggest that there have been significant increases in various phytoplankton populations since 1928-1929(Bell and Elmetri 1995. We support the inference that the Low Isles studies should have been extended over a number of years to better validate the data; the original plan was to conduct a multi-year monitoring program but funds initially approved by GBRMPA were cut after the first year.Furnas et al. note there is no...

show abstract

Nitrogen fixation by Trichodesmium spp. in the Central and Northern Great Barrier Reef Lagoon:relative importance of the fixed-nitrogen load

Cited by 67 publications

References 11 publications

Population dynamics and environmental conditions affecting Trichodesmium spp. (filamentous cyanobacteria) blooms in the south–west lagoon of New Caledonia

Population dynamics and environmental conditions affecting Trichodesmium spp. (filamentous cyanobacteria) blooms in the south–west lagoon of New Caledonia

A simple, binary classification algorithm for the detection of Trichodesmium spp. within the Great Barrier Reef using MODIS imagery

Response to “Selective Evidence of Eutrophication in the Great Barrier Reef” by Furnas et al.

Contact Info

Product

Resources

About