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Variability in ultraplankton at the Porcupine Abyssal Plain study site

Variability in ultraplankton at the Porcupine Abyssal Plain study site
Variability in ultraplankton at the Porcupine Abyssal Plain study site
Observations of the ultraplankton (<5 ?m) are presented from a 4 day mesoscale survey centred on the Porcupine Abyssal Plain (PAP) study site (49°00’N 16°30’W), in July 2006. The organisms enumerated include two groups of phytoplankton, Synechococcus cyanobacteria, heterotrophic bacteria, large viruses, and two size classes of heterotrophic protist. The dataset comprises over 400 samples from the mixed layer taken over a 100 × 100 km2 area at a spatial resolution of typically 2-3 km.

For phytoplankton and heterotrophic bacteria there is a clear bimodal structure to the histograms of abundance indicative of two distinct communities in the region. Using the strong bimodality of one of the phytoplankton groups’ histogram as a basis, the dataset is split into two subsets, with roughly 200 points in each, corresponding to the two histogram peaks. Doing so provides evidence that Synechococcus and viruses may also have a bimodal structure. Correlations between all pairings of these five organisms (both phytoplankton groups, Synechococcus, heterotrophic bacteria and viruses) are positive and quite high (r>0.7). The two communities can therefore be characterised as high and low abundance. Although there is a coincidence of low abundances with high temperatures in the southwest corner of the region, where there was known to be an eddy present, the spatial distributions of these organisms over the whole region is poorly predicted by temperature (or salinity or density). Furthermore, the spatial distributions of heterotrophic protists are found to differ strongly from those of the other organisms, having a unimodal structure and no obvious large scale structure. The more random structure of the heterotrophs’ spatial distribution compared to their prey is consistent with previous results from the continental shelf, but is demonstrated for the open ocean here for the first time.

Spatial variability is a large potential source of error in point samples, such as those comprising time series or transect cruises, unless a sufficient number of samples are taken. This large dataset is further used to provide guidance on the number of samples that would be required to estimate the mean abundance for the organisms accurately in this spatially variable region. Even if the bimodal structure was known initially, many of the organisms would require 10 or more samples to estimate the mean with 25% accuracy.
0967-0645
1336-1345
Martin, Adrian P.
9d0d480d-9b3c-44c2-aafe-bb980ed98a6d
Zubkov, Mikhail V.
b1dfb3a0-bcff-430c-9031-358a22b50743
Holland, R
e64c15c4-91dd-4dcc-a97c-719fb280bbb9
Tarran, Glen
2784c8a8-2827-4403-a83b-2c12131c0998
Burkill, Peter
8de19a9f-88e1-4db8-b19a-aa9ec215dede
Martin, Adrian P.
9d0d480d-9b3c-44c2-aafe-bb980ed98a6d
Zubkov, Mikhail V.
b1dfb3a0-bcff-430c-9031-358a22b50743
Holland, R
e64c15c4-91dd-4dcc-a97c-719fb280bbb9
Tarran, Glen
2784c8a8-2827-4403-a83b-2c12131c0998
Burkill, Peter
8de19a9f-88e1-4db8-b19a-aa9ec215dede

Martin, Adrian P., Zubkov, Mikhail V., Holland, R, Tarran, Glen and Burkill, Peter (2010) Variability in ultraplankton at the Porcupine Abyssal Plain study site. [in special issue: Water Column and Seabed Studies at the PAP Sustained Observatory in the Northeast Atlantic] Deep Sea Research Part II: Topical Studies in Oceanography, 57 (15), 1336-1345. (doi:10.1016/j.dsr2.2010.01.010).

Record type: Article

Abstract

Observations of the ultraplankton (<5 ?m) are presented from a 4 day mesoscale survey centred on the Porcupine Abyssal Plain (PAP) study site (49°00’N 16°30’W), in July 2006. The organisms enumerated include two groups of phytoplankton, Synechococcus cyanobacteria, heterotrophic bacteria, large viruses, and two size classes of heterotrophic protist. The dataset comprises over 400 samples from the mixed layer taken over a 100 × 100 km2 area at a spatial resolution of typically 2-3 km.

For phytoplankton and heterotrophic bacteria there is a clear bimodal structure to the histograms of abundance indicative of two distinct communities in the region. Using the strong bimodality of one of the phytoplankton groups’ histogram as a basis, the dataset is split into two subsets, with roughly 200 points in each, corresponding to the two histogram peaks. Doing so provides evidence that Synechococcus and viruses may also have a bimodal structure. Correlations between all pairings of these five organisms (both phytoplankton groups, Synechococcus, heterotrophic bacteria and viruses) are positive and quite high (r>0.7). The two communities can therefore be characterised as high and low abundance. Although there is a coincidence of low abundances with high temperatures in the southwest corner of the region, where there was known to be an eddy present, the spatial distributions of these organisms over the whole region is poorly predicted by temperature (or salinity or density). Furthermore, the spatial distributions of heterotrophic protists are found to differ strongly from those of the other organisms, having a unimodal structure and no obvious large scale structure. The more random structure of the heterotrophs’ spatial distribution compared to their prey is consistent with previous results from the continental shelf, but is demonstrated for the open ocean here for the first time.

Spatial variability is a large potential source of error in point samples, such as those comprising time series or transect cruises, unless a sufficient number of samples are taken. This large dataset is further used to provide guidance on the number of samples that would be required to estimate the mean abundance for the organisms accurately in this spatially variable region. Even if the bimodal structure was known initially, many of the organisms would require 10 or more samples to estimate the mean with 25% accuracy.

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Published date: 1 August 2010
Organisations: Marine Biogeochemistry

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Local EPrints ID: 158537
URI: http://eprints.soton.ac.uk/id/eprint/158537
ISSN: 0967-0645
PURE UUID: 8f36dbb1-b6cb-4a8a-93dd-43105b024c19

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Date deposited: 21 Jun 2010 13:58
Last modified: 14 Mar 2024 01:51

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Contributors

Author: Adrian P. Martin
Author: Mikhail V. Zubkov
Author: R Holland
Author: Glen Tarran
Author: Peter Burkill

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