scholarly journals Spring net community production and its coupling with the CO<sub>2</sub> dynamics in the surface water of the northern Gulf of Mexico

2019 ◽  
Vol 16 (18) ◽  
pp. 3507-3525
Author(s):  
Zong-Pei Jiang ◽  
Wei-Jun Cai ◽  
John Lehrter ◽  
Baoshan Chen ◽  
Zhangxian Ouyang ◽  
...  
Keyword(s):  
Surface Water ◽  
Gulf Of Mexico ◽  
Mississippi River ◽  
Phytoplankton Production ◽  
Biological Production ◽  
Net Community Production ◽  
Northern Gulf Of Mexico ◽  
Co2 Sink ◽  
Community Production

Abstract. Net community production (NCP) in the surface water of the northern Gulf of Mexico (nGOM) and its coupling with the CO2 system were examined during the productive spring season. NCP was estimated using multiple approaches: (1) underway O2 and Ar ratio, (2) oxygen changes during light/dark bottle oxygen incubations, and (3) non-conservative changes in dissolved inorganic carbon or nutrients. These methods all showed high spatial variability of NCP and displayed similar patterns along the river–ocean mixing gradient, showing high production rates in plume regions. NCPO2Ar estimated from high-resolution O2 and Ar underway measurement indicated heterotrophic conditions at the high-nutrient and high-turbidity Mississippi River end (-51.3±11.9 mmol C m−2 d−1 when salinity < 2) resulting from the influence of terrestrial carbon input and light limitation on photosynthesis. High NCPO2Ar rates (105.0±59.2 mmol C m−2 d−1, up to 235.4 mmol C m−2 d−1) were observed in the Mississippi and Atchafalaya plumes at intermediate salinities between 15 and 30 where light and nutrients were both favorable for phytoplankton production. NCPO2Ar rates observed in the high-salinity, oligotrophic offshore waters (salinity > 35.5) were close to zero due to nutrient limitation. Air–sea CO2 fluxes generally showed corresponding changes, from being a strong CO2 source in the river channel (55.5±7.6 mmol C m−2 d−1), to a CO2 sink in the plume (-13.4±5.5 mmol C m−2 d−1), and to being nearly in equilibrium with the atmosphere in offshore waters. Overall, the surface water of the nGOM was net autotrophic during spring 2017, with an area-weighted mean NCPO2Ar of 21.2 mmol C m−2 d−1, and was a CO2 sink of −6.7 mmol C m−2 d−1. A temporal mismatch between in situ biological production and gas exchange of O2 and CO2 was shown through a box model to result in decoupling between NCPO2Ar and CO2 flux (e.g., autotrophic water as a CO2 source outside the Mississippi River mouth and heterotopic water as a CO2 sink in the Atchafalaya coastal water). This decoupling was a result of in situ biological production superimposed on the lingering background pCO2 from the source water because of the slow air–sea CO2 exchange rate and the buffering effect of the carbonate system.

scholarly journals Spring net community production and its coupling with the CO<sub>2</sub> dynamics in the surface water of the northern Gulf of Mexico

2019 ◽  
Author(s):  
Zong-Pei Jiang ◽  
Wei-Jun Cai ◽  
John Lehrter ◽  
Baoshan Chen ◽  
Zhangxian Ouyang ◽  
...  
Keyword(s):  
Surface Water ◽  
Gulf Of Mexico ◽  
Co2 Fluxes ◽  
Spring Season ◽  
Biological Production ◽  
Net Community Production ◽  
Northern Gulf Of Mexico ◽  
Co2 Sink ◽  
Community Production

Abstract. Net community production (NCP) in the surface mixed layer of the northern Gulf of Mexico (nGOM) and its coupling with the CO2 system were examined during the productive spring season. NCP was estimated using multiple approaches: (1) underway O2 and Ar ratio, (2) light/dark bottle oxygen incubations, and (3) non-conservative changes in dissolved inorganic carbon and nutrients; in order to assess uncertainties and compare the temporal-spatial scales associated with the different approaches. NCP estimates derived from various methods showed similar pattern along the river-ocean mixing gradient. The NCPO2Ar estimated from the high resolution O2 and Ar underway measurement is characterized by negative rates (−25.4 mmol C m−2 d−1) at the high nutrient and high turbidity river end (salinity  31) oligotrophic offshore waters due to nutrient limitation. Air-sea CO2 fluxes generally showed corresponding changes from being a strong CO2 source in the river channel to a CO2 sink in the plume. CO2 fluxes were near zero in offshore waters indicating balanced autotrophy and heterotrophy at these sites. Overall, the surface water in the nGOM (93–89.25° W, 28.5–29.5° N) was strongly autotrophic during the spring season in spring 2017 with mean NCP rate of 21.2 mmol C m−2 d−1 and as a CO2 sink of −6.7 mmol C m−2 d−1. By using a 1-D model, we demonstrated that a temporal mismatch between in situ biological production and gas exchange of O2 and CO2 could result in decoupling between NCP and CO2 flux (e.g., autotropic water as a CO2 source outside the Mississippi river mouth and heterotopic water as a CO2 sink near the Atchafalaya Delta). This decoupling was a result of in situ biological production superimposed on the lingering background pCO2 from the source water because of the slow air-sea CO2 exchange rate and buffering effect of the carbonate system.

scholarly journals Neural network-based estimates of Southern Ocean net community production from in situ O<sub>2</sub> / Ar and satellite observation: a methodological study

2014 ◽  
Vol 11 (12) ◽  
pp. 3279-3297 ◽  
Author(s):  
C.-H. Chang ◽  
N. C. Johnson ◽  
N. Cassar
Keyword(s):  
Neural Network ◽  
Organic Carbon ◽  
Southern Ocean ◽  
Mixed Layer ◽  
Sea Surface ◽  
Carbon Export ◽  
Net Community Production ◽  
Basin Scale ◽  
Community Production

Abstract. Southern Ocean organic carbon export plays an important role in the global carbon cycle, yet its basin-scale climatology and variability are uncertain due to limited coverage of in situ observations. In this study, a neural network approach based on the self-organizing map (SOM) is adopted to construct weekly gridded (1° × 1°) maps of organic carbon export for the Southern Ocean from 1998 to 2009. The SOM is trained with in situ measurements of O2 / Ar-derived net community production (NCP) that are tightly linked to the carbon export in the mixed layer on timescales of one to two weeks and with six potential NCP predictors: photosynthetically available radiation (PAR), particulate organic carbon (POC), chlorophyll (Chl), sea surface temperature (SST), sea surface height (SSH), and mixed layer depth (MLD). This nonparametric approach is based entirely on the observed statistical relationships between NCP and the predictors and, therefore, is strongly constrained by observations. A thorough cross-validation yields three retained NCP predictors, Chl, PAR, and MLD. Our constructed NCP is further validated by good agreement with previously published, independent in situ derived NCP of weekly or longer temporal resolution through real-time and climatological comparisons at various sampling sites. The resulting November–March NCP climatology reveals a pronounced zonal band of high NCP roughly following the Subtropical Front in the Atlantic, Indian, and western Pacific sectors, and turns southeastward shortly after the dateline. Other regions of elevated NCP include the upwelling zones off Chile and Namibia, the Patagonian Shelf, the Antarctic coast, and areas surrounding the Islands of Kerguelen, South Georgia, and Crozet. This basin-scale NCP climatology closely resembles that of the satellite POC field and observed air–sea CO2 flux. The long-term mean area-integrated NCP south of 50° S from our dataset, 17.9 mmol C m−2 d−1, falls within the range of 8.3 to 24 mmol C m−2 d−1 from other model estimates. A broad agreement is found in the basin-wide NCP climatology among various models but with significant spatial variations, particularly in the Patagonian Shelf. Our approach provides a comprehensive view of the Southern Ocean NCP climatology and a potential opportunity to further investigate interannual and intraseasonal variability.

Validating the occurrence of Caribbean reef sharks, Carcharhinus perezi (Poey), (Chondrichthyes: Carcharhiniformes) in the northern Gulf of Mexico, with a key for sharks of the family Carcharhinidae inhabiting the region

Zootaxa ◽  
2011 ◽  
Vol 2933 (1) ◽  
pp. 65 ◽  
Author(s):  
WILLIAM B. DRIGGERS III ◽  
ERIC R. HOFFMAYER ◽  
EMMA L. HICKERSON ◽  
TIMOTHY L. MARTIN ◽  
CHRISTOPHER T. GLEDHILL
Keyword(s):  
Gulf Of Mexico ◽  
North Atlantic ◽  
Mississippi River ◽  
North Atlantic Ocean ◽  
Shark Species ◽  
Mississippi River Delta ◽  
The Bahamas ◽  
Northern Gulf Of Mexico ◽  
The Family ◽  
Reef Sharks

Among the sharks inhabiting the continental shelf waters of the western North Atlantic Ocean, those within the genus Carcharhinus are the most speciose (Castro 2011). Authoritative sources agree on the presence of twelve species of carcharhinids in the northern Gulf of Mexico; however, they disagree on the presence of a thirteenth species, C. perezi (Poey), in the region (Compagno 1984, Compagno 2002, McEachran & Fechhelm 1998, Castro 2011). While the range of C. perezi is well-documented to extend from the southeastern coast of Florida and the Bahamas to Brazil (Castro 2011), published records of C. perezi occurring in the northern Gulf of Mexico are limited to two sources. In their description of Eulamia springeri, a junior synonym of C. perezi, Bigelow & Schroeder (1944) place the species in the northern Gulf of Mexico based on “a somewhat shrivelled skin with head” from a specimen collected off the west coast of Florida that was reported by the authors to be “probably of this species.” Later, Springer (1960) reported the capture of a single specimen off the Mississippi River Delta in 1947; however, no detail of the capture was provided other than it being listed within a table summarizing shark species collected during exploratory fishing operations.

scholarly journals Extensive reproductive disruption, ovarian masculinization and aromatase suppression in Atlantic croaker in the northern Gulf of Mexico hypoxic zone

2011 ◽  
Vol 279 (1726) ◽  
pp. 28-38 ◽  
Author(s):  
Peter Thomas ◽  
Md. Saydur Rahman
Keyword(s):  
Gulf Of Mexico ◽  
Mississippi River ◽  
Aromatase Activity ◽  
Northern Gulf Of Mexico ◽  
Hypoxia Exposure ◽  
Hypoxic Zone ◽  
Seasonal Hypoxia ◽  
Reproductive Disruptions ◽  
Reproductive Disruption

The long-term impacts on marine ecosystems of the recent dramatic worldwide increase in the incidence of coastal hypoxia are unknown. Here, we show widespread reproductive disruption in Atlantic croakers collected from hypoxic sites approximately 120 km apart in the extensive northern Gulf of Mexico continental shelf hypoxic zone. Gonadal growth and gamete production were impaired in croakers from hypoxic sites compared with fish from reference normoxic sites east of the Mississippi River Delta. Male germ cells were detected in approximately 19 per cent of croaker ovaries collected in the hypoxic region, but were absent in ovaries from normoxic sites. In addition, the sex ratio was skewed towards males at the hypoxic sites. The masculinization and other reproductive disruptions were associated with declines in neuroendocrine function, as well as ovarian and brain expression of aromatase (the enzyme that converts androgens to oestrogens). A similar incidence of ovarian masculinization and decline in ovarian aromatase expression were observed in croaker after chronic laboratory hypoxia exposure, indicating that ovarian masculinization is a specific hypoxia response and is due to decreased aromatase activity. The results suggest severe reproductive impairment can occur over large coastal regions in marine fish populations exposed to seasonal hypoxia, with potential long-term impacts on population abundance.

Sign in / Sign up

Export Citation Format

Share Document