Fish landings and Oman shelf area
Sergey A. Piontkovski1, H.E. Hamed S. Al-Oufi2, and Nadir M. Al-Abri2
1Sultan Qaboos University, College of Agricultural and Marine Sciences, Dpt. of Marine Science and Fisheries.
2 Ministry of Agriculture and Fisheries Wealth. PO 467, Muscat 113.
Sultanate of Oman.
Data from five field surveys carried out along the shelf in the 20-250m depth range and historical data on artisanal fishery were analyzed. A positive linear relationship between the demersal fish biomass and the shelf area was pronounced for a certain (intermediate) stratum only: 50-100m. No statistical link was found for the strata above it (25-50m) and beneath it (100-150m and 150-250m). The pronounced one was associated with the low boundary of the oxygen minimum zone impinging on the shelf. Annual landings of demersal fishes in the region with the largest shelf area exceeded landings in the region with the smallest area by as much as 1.6 times. The ratio of small pelagic to demersal fish landings decreased as a factor of 10, from small to large shelf areas.
Fish landings; Arabian Sea; continental shelf; oxygen minimum zone; Oman
Subsurface algal blooms of the northwestern Arabian Sea
Sergey A. Piontkovski1,*, Bastien Y. Queste2, Khalid A. Al-Hashmi1, Aisha Al-Shaaibi1, Yulia V. Bryantseva3, Elena A. Popova4
1College of Agricultural and Marine Sciences, Sultan Qaboos University, PO Box 34, Al-Khod 123, Sultanate of Oman
2Centre for Ocean and Atmospheric Sciences, University of East Anglia, Norwich NR4 7TJ, UK
3M.G. Kholodny Institute of Botany, 2 Terechenkovskaya Str., Kiev 01030, Ukraine
4Institute of Marine Biological Research, 2 Nakhimov Prospect, P.O. Box 229011, Russia
In situ plankton sampling, combined with remotely sensed and ocean Seaglider observations, provided insight into the termination of the winter monsoon bloom and subsequent evolution into a subsurface fluorescence maximum in the northwestern Arabian Sea. This sub - surface maximum gradually descended, presenting increased fluorescence between 25 and 55 m depth during the spring inter-monsoon season. Species diversity decreased by half within the deep fluorescence maximum relative to the bloom. The dinoflagellate Noctiluca scintillans dominated by biomass in all samples collected from the depth of the subsurface fluorescence maximum. We show that the subsurface algal bloom persists throughout inter-monsoon seasons, linking algal blooms initiated during the southwest and northeast monsoons. In situ samples showed a net decrease in Noctiluca cell size, illustrating a shift towards a deep chlorophyll maximum adapted community, but did not exhibit any increases in chlorophyll-containing endo - symbionts. We propose that the plankton biomass and estimates of the northwestern Arabian Sea productivity are much greater than estimated previously through remote sensing observations, due to the persistence, intensity and vertical extent of the deep chlorophyll maximum which— using remote means—can only be estimated, but not measured.
KEY WORDS: Algal blooms · Chlorophyll a · Zooplankton
A global diatom database – abundance, biovolume and biomass in the world ocean
K. Leblanc1, J. Ar´ıstegui2, L. Armand3, P. Assmy4, B. Beker5, A. Bode6, E. Breton7,8,9, V. Cornet1, J. Gibson10, M.-P. Gosselin11, E. Kopczynska12, H. Marshall13, J. Peloquin14, S. Piontkovski15, A. J. Poulton16, B. Qu´eguiner1, R. Schiebel17, R. Shipe18, J. Stefels19, M. A. van Leeuwe19, M. Varela6, C. Widdicombe20, and M. Yallop21
1Aix-Marseille Universit´e, Universit´e du Sud Toulon-Var, CNRS/INSU, IRD, MIO, UM 110, 13288, Marseille, Cedex 09, France
2Instituto de Oceanograf´ıa y Cambio Global, Universidad de Las Palmas de Gran Canaria, 35017 Las Palmas Spain
3Department of Biological Sciences, Macquarie University, North Ryde, NSW, 2109, Australia
4Norwegian Polar Institute, Fram Centre, Hjalmar Johansens gt. 14, 9296 Tromsø, Norway
5Laboratoire des Sciences de l’Environnement Marin, UMR6539, CNRS, Institut Universitaire Europ´een de la Mer (IUEM), Place Nicolas Copernic, Technopˆole Brest Iroise, 29280 Plouzan´e, France
6Instituto Espa˜nol de Oceanograf´ıa, Centro Oceanogr´afico de A Coru˜na Apdo. 130, 15080, A Coru˜na, Spain
7Univ Lille Nord de France, 59000 Lille, France
8ULCO, LOG, 62930 Wimereux, France
9CNRS, UMR8187 LOG, 62930 Wimereux, France
10Institute for Marine and Antarctic Studies, University of Tasmania, Private Bag 129, Hobart, Tasmania 7001,
11The Freshwater Biological Association, The Ferry Landing, Far Sawrey, Ambleside, LA22 0LP, UK
12Institute of Biochemistry and Biophysics, Department of Antarctic Biology, Polish Academy of Sciences,
02-141 Warszawa, Poland
13Department of Biological Sciences, Old Dominion University, Norfolk, VA, USA
14Inst. f. Biogeochemie u. Schadstoffdynamik, Universit¨atstrasse 16, 8092 Z¨urich, Switzerland
15Department of Marine Sciences, Sultan Qaboos University, Sultanate of Oman
16National Oceanography Centre, Waterfront Campus, Southampton, SO14 3ZH, UK
17Laboratoire des Bio-Indicateurs Actuels et Fossiles (BIAF), UPRES EA 2644, Universit´e d’Angers, 49045
Angers CEDEX 01, France
18UCLA, Los Angeles, California 90095, USA
19University of Groningen, Centre for Life Sciences Ecophysiology of Plants, P.O. Box 11103, 9700 CC
Groningen, The Netherlands
20Plymouth Marine Laboratory, Prospect Place, West Hoe, Plymouth, PL1 3DH, UK
21School of Biological Sciences, University of Bristol, Woodland Road, Bristol BS8 1UG, UK
Phytoplankton identification and abundance data are now commonly feeding plankton distribution databases worldwide. This study is a first attempt to compile the largest possible body of data available from different databases as well as from individual published or unpublished datasets regarding diatom distribution in the world ocean. The data obtained originate from time series studies as well as spatial studies. This effort is supported by the Marine Ecosystem Model Inter-Comparison Project (MAREMIP), which aims at building consistent datasets for the main plankton functional types (PFTs) in order to help validate biogeochemical ocean models by using carbon (C) biomass derived from abundance data. In this study we collected over 293 000 individual geo-referenced data points with diatom abundances from bottle and net sampling. Sampling site distribution was not homogeneous, with 58% of data in the Atlantic, 20% in the Arctic, 12% in the Pacific, 8% in the Indian and 1% in the Southern Ocean. A total of 136 different genera and 607 different species were identified after spell checking and name correction. Only a small fraction of these data were also documented for biovolumes and an even smaller fraction was converted to C biomass. As it is virtually impossible to reconstruct everyone’s method for biovolume calculation, which is usually not indicated in the datasets, we decided to undertake the effort to document, for every distinct species, the minimum and maximum cell dimensions, and to convert all the available abundance data into biovolumes and C biomass using a single standardized method. Statistical correction of the database was also adopted to exclude potential outliers and suspicious data points. The final database contains 90 648 data points with converted C biomass. Diatom C biomass calculated from cell sizes spans over eight orders of magnitude. The mean diatom biomass for individual locations, dates and depths is 141.19 μg Cl−1, while the median value is 11.16 μg Cl−1. Regarding biomass distribution, 19% of data are in the range 0–1 μg Cl−1, 29% in the range 1–10 μg Cl−1, 31% in the range 10–100 μg Cl−1, 18% in the range 100–1000 μg Cl−1, and only 3% > 1000 μg Cl−1. Interestingly, less than 50 species contributed to >90% of global biomass, among which centric species were dominant. Thus, placing significant efforts on cell size measurements, process studies and C quota calculations of these species should considerably improve biomass estimates in the upcoming years. A first-order estimate of the diatom biomass for the global ocean ranges from 444 to 582 Tg C, which converts to 3 to 4 Tmol Si and to an average Si biomass turnover rate of 0.15 to 0.19 d−1.
Link to the dataset: