Abstract The distribution of dissolved organic carbon (DOC) concentration across coastal waters was characterized based on the compilation of 3510 individual estimates of DOC in coastal waters worldwide. We estimated the DOC concentration in the coastal waters that directly exchange with open ocean waters in two different ways, as the DOC concentration at the edge of the shelf break and as the DOC concentration in coastal waters with salinity close to the average salinity in the open ocean. Using these estimates of DOC concentration in the coastal waters that directly exchange with open ocean waters, the mean DOC concentration in the open ocean and the estimated volume of water annually exchanged between coastal and open ocean, we estimated a median ± SE (and average ± SE) global DOC export from coastal to open ocean waters ranging from 4.4 ± 1.0 Pg C yr −1 to 27.0 ± 1.8 Pg C yr −1 (7.0 ± 5.8 Pg C yr −1 to 29.0 ± 8.0 Pg C yr −1 ) depending on the global hydrological exchange. These values correspond to a median and mean median (and average) range between 14.7 ± 3.3 to 90.0 ± 6.0 (23.3 ± 19.3 to 96.7 ± 26.7) Gg C yr −1 per km of shelf break, which is consistent with the range between 1.4 to 66.1 Gg C yr −1 per km of shelf break of available regional estimates of DOC export. The estimated global DOC export from coastal to open ocean waters is also consistent with independent estimates of the net metabolic balance of the coastal ocean. The DOC export from the coastal to the open ocean is likely to be a sizeable flux and is likely to be an important term in the carbon budget of the open ocean, potentially providing an important subsidy to support heterotrophic activity in the open ocean.
Jellyfish (Cnidaria, Scyphozoa) blooms appear to be increasing in both intensity and frequency in many coastal areas worldwide, due to multiple hypothesized anthropogenic stressors. Here, we propose that the proliferation of artificial structures – associated with (1) the exponential growth in shipping, aquaculture, and other coastal industries, and (2) coastal protection (collectively, “ocean sprawl”) – provides habitat for jellyfish polyps and may be an important driver of the global increase in jellyfish blooms. However, the habitat of the benthic polyps that commonly result in coastal jellyfish blooms has remained elusive, limiting our understanding of the drivers of these blooms. Support for the hypothesized role of ocean sprawl in promoting jellyfish blooms is provided by observations and experimental evidence demonstrating that jellyfish larvae settle in large numbers on artificial structures in coastal waters and develop into dense concentrations of jellyfish‐producing polyps.
Warming over Antarctica is leading to changes in the zooplankton communities inhabiting the Southern Ocean. It has been observed that zooplankton not only regulates phytoplankton through grazing, but also through the recycling of nutrients that are essential for phytoplankton growth. In this way, the effects of warming on zooplankton populations will change the amount or proportion at which recycled nutrients are restored. To estimate how the recycled nutrients released by zooplankton populations, dominated by krill (Euphausia superba), amphipods or copepods, affect the phytoplankton uptake and communities, we performed four incubation experiments: two close to the Antarctic Peninsula and two at the Southern Atlantic Ocean. Our results showed a stimulating effect of the addition of metabolites on ammonia removal rates and on the net growth of phytoplankton communities, with different responses amongst the different phytoplankton groups. According to our results, phytoplankton net growth and community composition may be altered if this relevant source of nutrients is lost due to projected changes in the abundance or distribution of these zooplankton populations.
Aerial images of inner Kobbefjord (SW Greenland) were acquired on two occasions in 2018 (2018-09-07 15:06; 2018-09-07 16:00) representing different tidal levels and on one occasion in 2019 (2019-08-26). Images were acquired using a DJI Mavic Air drone. The imagery was acquired in connection with the “Greenland Ecosystem Monitoring Program” “Nuuk Basis” monitoring of marine flora (http://g-e-m.dk/). This drone survey was carried out with the primary goal of documenting and quantifying the area distribution of the tidal vegetation (dominated by the brown macroalga <em>Ascophyllum nodosum</em>) and shallow subtidal vegetation at the monitoring site. Images were processed using Agisoft Metashape Professional to produce high resolution orthomosaics from each UAV survey.
The role of saline lakes in CO 2 exchange with the atmosphere was evaluated on the basis of calculated partial pressure ( p CO 2 ) and CO 2 exchange rates with the atmosphere derived from a compilation of published data for 196 saline lakes around the world. The average surface water p CO 2 exceeded atmospheric p CO 2 by a factor of 5–8 times, indicative of a tendency for saline lakes to emit CO 2 to the atmosphere. Chemically enhanced emission, calculated from solute chemistry, pH, and wind speed, increased gas exchange an average of 2.3 times over that of freshwater lakes having equivalent p CO 2 . The globally distributed lakes emitted CO 2 at rates in excess of 80 mmol m −2 d −1 . The Caspian Sea was calculated to support alone a total CO 2 emission of 0.02 to 0.04 Gt C a −1 , with the total CO 2 emissions to the atmosphere from saline lakes calculated to be 0.11–0.15 Gt C a −1 . Consideration of CO 2 emissions from saline lakes raises the total CO 2 emissions to the atmosphere from all lakes to 0.28–0.32 Gt CO 2 . These results point to a significant role of saline lakes in global C cycling.
Exotic species often face new environmental conditions that are different from those that they are adapted to. The tropical seagrass Halophila stipulacea is a Lessepsian migrant that colonized the Mediterranean Sea around 100 years ago, where at present the minimum seawater temperature is cooler than in its native range in the Red Sea. Here, we tested if the temperature range in which H. stipulacea can exist is conserved within the species or if the exotic populations have shifted their thermal breadth and optimum due to the cooler conditions in the Mediterranean. We did so by comparing the thermal niche (e.g. optimal temperatures, and upper and lower thermal limits) of native (Saudi Arabia in the Red Sea) and exotic (Greece and Cyprus in the Mediterranean Sea) populations of H. stipulacea. We exposed plants to 12 temperature treatments ranging from 8 to 40°C for 7 days. At the end of the incubation period, we measured survival, rhizome elongation, shoot recruitment, net population growth and metabolic rates. Upper and lower lethal thermal thresholds (indicated by 50% plant mortality) were conserved across populations, but minimum and optimal temperatures for growth and oxygen production were lower for Mediterranean populations than for the Red Sea one. The displacement of the thermal niche of exotic populations towards the colder Mediterranean Sea regime could have occurred within 175 clonal generations.
Abstract. The role of seagrass, Posidonia oceanica, meadows as a source of transparent exopolymer particles (TEP) to Mediterranean coastal waters was tested by comparing the TEP dynamics in two adjacent coastal waters in the oligotrophic NW Mediterranean Sea, one characterized by oligotrophic open-sea waters and the other accumulating seagrass leaf litter, together with an experimental examination of TEP release by seagrass litter. TEP concentrations ranged from 4.6 µg XG Eq L−1 to 90.6 µg XG Eq L−1, with mean (±SE) values of 38.7 (±2.02) µg XG Eq L−1 in the site devoid of seagrass litter, whereas the coastal beach site accumulating leaf litter had > 10-fold mean TEP concentrations of 487.02 (±72.8) µg XG Eq L−1 . Experimental evaluation confirmed high rates of TEP production by P. oceanica litter, allowing calculations of the associated TEP yield. We demonstrated that P. oceanica is an important source of TEP to the Mediterranean Sea, contributing an estimated 0.10 Tg C as TEP annually. TEP release by P. oceanica seagrass explains the elevated TEP concentration relative to the low chlorophyll a concentration in the Mediterranean Sea.
MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 262:43-53 (2003) - doi:10.3354/meps262043 Alkaline phosphatase activities in the central Atlantic Ocean indicate large areas with phosphorus deficiency Montserrat Vidal1,*, Carlos M. Duarte2, Susana Agustí2, Josep M. Gasol3, Dolors Vaqué3 1Departament d¹Ecologia, Universitat de Barcelona, Avinguda Diagonal 645, 08028 Barcelona, Spain 2Institut Mediterrani d¹Estudis Avançats (CSIC-UIB), C/ Miquel Marqués 21, 07190 Esporles (Illes Balears), Spain 3Institut de Ciències del Mar (CMIMA-CSIC), Passeig Marítim de la Barceloneta 37-49, 08003 Barcelona, Spain *Email: montsevidal@ub.edu ABSTRACT: The activity of the enzyme alkaline phosphatase (APA) was studied along 2 latitudinal transects in the central Atlantic (28°S to 28°N) and compared to the distribution of nutrient concentrations, planktonic biomass and other variables reflecting community P status. Using 3-0-methyl fluorescein phosphate (MF-P), APA was measured fluorometrically in 2 size fractions (<0.8 and <150 µm) and in the dissolved fraction (i.e. that fraction passing through 0.2 µm filters). Significant APA (p < 0.05) was recorded over extensive areas of the central Atlantic, ranging from 4 to 50 nmol MF-P l-1 h-1. Most activity arose from the free dissolved fraction, followed by the <0.8 µm size fraction. The relatively low APA in the central Atlantic is due to the low biomass that characterises most of the area covered by the transects. Nevertheless, the specific activity per unit biomass was high in both the north and south Atlantic subtropical gyres in this area. Along the transects, APA displayed an inverse relationship to the calculated upward turbulent nutrient fluxes. The results support the existence of persistent P-limited conditions in much of the central Atlantic Ocean. This is consistent with stoichiometric data and estimated rate processes and fluxes in the area, indicating that P regeneration from dissolved organic phosphorus may play an important role in the central Atlantic, allowing efficient utilisation of P in the biogenic layer and avoiding P loss through the diffusive vertical flux of dissolved organic matter that preferentially removes C and N. KEY WORDS: Alkaline phosphatase activity · Atlantic Ocean · Phosphorus deficiency · Enzyme activity Full text in pdf format Supplementary Appendix PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 262. Online publication date: November 07, 2003 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2003 Inter-Research.
