112
Chapter 7: Provinces: The Secondary Compartments
110
of latitude. In this case, shipboard observations of water properties to 200 m were
used to identify geographic discontinuities by means of derivative analysis. The authors
suggest that the results validate the concept of biogeochemical provinces discussed here.
An independent test using the same techniques from derivative analysis were run with
remotely sensed sea-surface bio-optical data obtained from SeaWiFS gave the same result
and identified the same province boundaries. The results obtained in this investigation
were almost entirely supportive of the partition suggested here for the open Atlantic
Ocean—NADR, NAST, NATR, WTRA, and SATL.
Biogeographic Tests
Alain Fonteneau investigated the distribution of all species of tuna in the records maintained by the Inter-American Tropical Tuna Commission in La Jolla, California, and
elsewhere, in order to model trophic chains on the high seas. He found a singular concordance between distribution of different species and the boundaries of the provinces
proposed here. He remarks, for instance, that there is an excellent concordance between
the distribution of yellowfin (Thunnus albacares) and skipjack (Katsuwonus pelamis) distributions and the equatorial provinces—PNEC and PEQD in the Pacific and ETRA
and WTRA in the Atlantic Ocean. It is all the more remarkable that this should be so,
given the extraordinary mobility of oceanic tuna, their very extensive migrations, and the
independence of the various integrated data sets. I shall make repeated reference to the
ORSTOM tuna atlas that embodies his analysis (Fontenau, 1997).
Accumulated data on the distribution of euphausiids in the South Atlantic were used
by Gibbons (1997) to test the congruence between the partition of classical biogeography
discussed in Chapter 2 into climatic zones (Tropical, Subtropical, Temperate, and so on)
and those proposed in early versions of the biogeographical partition discussed here. The
test was performed both with all species and also with epipelagic species alone. Using BrayCurtis clustering techniques, six groups were obtained for all species (Tropical, Warm
and Cold Temperate, Subantarctic, and Antarctic) together with and two local groups
of epipelagic species (Benguelan and offshore Falkland regions). Gibbons comments
that congruence is good between the distributions of these groups and biogeochemical
provinces in the south, but poor in the north and coastal regions. Given (i) the static
location of Gibbons data points and the dynamic location of province boundaries and
(ii) the stronger and more predictable pattern of province boundaries in the Southern
Ocean than farther north, this is a predictable result.
The largest biogeographical data base that has been applied to verification of the
provinces discussed here is, of course, that of Hardy’s Continuous Plankton Recorder
(CPR) by Beaugrand and his colleagues at Plymouth (e.g., Beaugrand et al., 2002a,b).
Although the available data points are extremely numerous (>18 × 10
−6 to date) they are
not ideally disposed in the open ocean for the purpose, being mostly along “great circle”
routes between the UK and North American ports; over the shelf and adjacent regions
of the NE Atlantic, they are closer to ideal. The CPR data for calanoid copepods were
processed for taxonomic richness and for the occurrence of some 96 taxa, partitioned
between day and night samples; Bray-Curtis clustering is followed by a complete linkage
clustering technique that offers several cut-off levels of indicator values: using the first
eight cutoff levels, a dendrogram comprising 15 species clusters was obtained, each of
which mapped coherently into a specific region of the North Atlantic. Of these, several
appear to represent transitions between other clusters and are interpreted as ecotones—
either between two oceanic clusters or between shelf and oceanic regions.
The first cutoff level (0.5) separated the Arctic biome from the Westerly Winds biome
and suggested a boundary between them that was consistent with that used here; also
consistent was the relative diversity—4 indicator species in the former, 58 in the latter.
Chapter 7: Provinces: The Secondary Compartments
110
of latitude. In this case, shipboard observations of water properties to 200 m were
used to identify geographic discontinuities by means of derivative analysis. The authors
suggest that the results validate the concept of biogeochemical provinces discussed here.
An independent test using the same techniques from derivative analysis were run with
remotely sensed sea-surface bio-optical data obtained from SeaWiFS gave the same result
and identified the same province boundaries. The results obtained in this investigation
were almost entirely supportive of the partition suggested here for the open Atlantic
Ocean—NADR, NAST, NATR, WTRA, and SATL.
Biogeographic Tests
Alain Fonteneau investigated the distribution of all species of tuna in the records maintained by the Inter-American Tropical Tuna Commission in La Jolla, California, and
elsewhere, in order to model trophic chains on the high seas. He found a singular concordance between distribution of different species and the boundaries of the provinces
proposed here. He remarks, for instance, that there is an excellent concordance between
the distribution of yellowfin (Thunnus albacares) and skipjack (Katsuwonus pelamis) distributions and the equatorial provinces—PNEC and PEQD in the Pacific and ETRA
and WTRA in the Atlantic Ocean. It is all the more remarkable that this should be so,
given the extraordinary mobility of oceanic tuna, their very extensive migrations, and the
independence of the various integrated data sets. I shall make repeated reference to the
ORSTOM tuna atlas that embodies his analysis (Fontenau, 1997).
Accumulated data on the distribution of euphausiids in the South Atlantic were used
by Gibbons (1997) to test the congruence between the partition of classical biogeography
discussed in Chapter 2 into climatic zones (Tropical, Subtropical, Temperate, and so on)
and those proposed in early versions of the biogeographical partition discussed here. The
test was performed both with all species and also with epipelagic species alone. Using BrayCurtis clustering techniques, six groups were obtained for all species (Tropical, Warm
and Cold Temperate, Subantarctic, and Antarctic) together with and two local groups
of epipelagic species (Benguelan and offshore Falkland regions). Gibbons comments
that congruence is good between the distributions of these groups and biogeochemical
provinces in the south, but poor in the north and coastal regions. Given (i) the static
location of Gibbons data points and the dynamic location of province boundaries and
(ii) the stronger and more predictable pattern of province boundaries in the Southern
Ocean than farther north, this is a predictable result.
The largest biogeographical data base that has been applied to verification of the
provinces discussed here is, of course, that of Hardy’s Continuous Plankton Recorder
(CPR) by Beaugrand and his colleagues at Plymouth (e.g., Beaugrand et al., 2002a,b).
Although the available data points are extremely numerous (>18 × 10
−6 to date) they are
not ideally disposed in the open ocean for the purpose, being mostly along “great circle”
routes between the UK and North American ports; over the shelf and adjacent regions
of the NE Atlantic, they are closer to ideal. The CPR data for calanoid copepods were
processed for taxonomic richness and for the occurrence of some 96 taxa, partitioned
between day and night samples; Bray-Curtis clustering is followed by a complete linkage
clustering technique that offers several cut-off levels of indicator values: using the first
eight cutoff levels, a dendrogram comprising 15 species clusters was obtained, each of
which mapped coherently into a specific region of the North Atlantic. Of these, several
appear to represent transitions between other clusters and are interpreted as ecotones—
either between two oceanic clusters or between shelf and oceanic regions.
The first cutoff level (0.5) separated the Arctic biome from the Westerly Winds biome
and suggested a boundary between them that was consistent with that used here; also
consistent was the relative diversity—4 indicator species in the former, 58 in the latter.