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North Carolina continental slope zoogeographical barrier
Deep-Sea Research, Vol. 26A, pp. 851 to 853 ~ Pergamon Press Ltd 1979 Printed in Great Britain
0011-7471/79/0701-0851 $02.00/0
NOTE
North Carolina continental slope zoogeographical barrier EDWARD B. CUTLER* and KAREN DOBLE* (Received 3 October 1978 ; in revised.lbrm 12 February 1979, accepted 12 February 1979)
Abstract--Collections of sipunculans and pogonophorans from depths between 150 and 2000 m around latitude 35°30'N were analyzed and used to supplement earlier information from this region. The addition of eight pogonophoran species from this area and minor revisions of earlier data reaffirm and strengthen the hypothesis that a zoogeographical barrier for slope dwelling infauna exists around 34°N off Cape Lookout, North Carolina.
IN 1975 Cutler suggested that a zoogeographical barrier for benthic infaunal invertebrates exists on the continental slope off Cape Lookout, North Carolina (34°N). This was based on an analysis of Sipuncula and Pogonophora distribution patterns in the area between 31040 ' and 36°19'N latitude at depths between 150 and 2500 m. This region was divided into 14 equal zones of 20-min intervals, then, based on presence or absence data, similarity coefficients were calculated and a cluster analysis was performed. It was noted that, "The peculiar nature of Zone 12 (35°20 ' to 35°39'N) is probably the result of only six stations being occupied there, yielding no pogonophorans and only five species of sipunculans." It was peculiar in that it did not group with the rest of the cluster until a similarity level of 27. None of the stations in Zone 12 was deeper than 500 m. It was evident that an unfortunate gap existed in the data so when the opportunity for an additional collecting trip on the R/V Eastward became available in July 1977, we returned to this region. We occupied five stations near 35°30'N at approximately 200, 500, 1000, 1500, and 2000 m. At each depth two collections were made using the Day (Capetown) Dredge and the Small Biological Trawl (see CUTLER, 1973, for details on technique). This particular area of the continental slope just north of Cape Hatteras is quite steep between 200 and 1500 m with irregular ridges and valleys. Several hauls revealed fine, black, apparently anaerobic sediments. Three stations in Zone 13 (35°40 ' to 35°59'N) were also made at 1000, 1500, and 2000 m to verify earlier finds there. No previously unreported species were found in Zone 13, so this has no effect on the hypothesis except additional confirmation. From Zone 12, of the five previously reported sipunculans, three were collected this time. The important feature is that eight pogonophoran species were collected over the range of depths from this zone for the first time (Appendix). In addition to this new material, E. C. Southward's reconsideration of some earlier collections (personal communication) led to several revisions of the pogonophoran data matrix: the lamellisabellids were separated into two species (yet undescribed); an unnamed Nereilinum species was added; Siboglinum holmei was removed and changes were made in S. gosnoldi and S. fulgens. The appendix shows only those species modified since CUTLER (1975, Appendix A). * Biology Department, Utica College of Syracuse University, Utica, NY 13502, U.S.A. 851
852
EDWARD B, CUTLER and KAREN DOBLE
STATIONS south
north 14 13 12 11 9
8
10734
52
--85 .-80
,,-75 0
,.-70 .-65
--60
-.55
I ,-50
Fig. 1. Dendogram showing results of group average cluster analysis on Dice's similarity coefficients for 14 zones.
With these new data, the numerical analysis was rerun using Dice's similarity coefficient and the group average cluster analysis. The reasons for using this coefficient were discussed in CUTLER(1975). BLANC,CHARDY, LAURECand REYS (1976) discussed Dice's coefficient along with several others, including Kulczinski's. SIBUET (1979) has used the Kulczinski 2 Index for her analysis of asteroid distribution as she has a high degree of heterogeneity in the number of species present in each area. That is not the case in our data, so we used Dice's coefficient believing in its continued validity. Zone 12 now pairs with Zones 9 and 11 at a similarity level greater than 70, creating a much more symmetrical dendrogram (Fig. 1). This work removes an apparent anomaly and strengthens the hypothesis set forth in CUTLER(1975) of a zoogeographical barrier for slope dwelling sedentary infauna around 34°N (more southerly for shallower species and more northerly for deeper species), the probable cause being the effects of bottom currents on larval dispersion. Acknowledgements--We are indebted to the officers and crew of the R/V Eastward, a group of colleagues who assisted in the collections, and NORMA CUTLER, who helped in several phases including the preparation of this manuscript. The continued interest and assistance of E. C. SOUTHWARD, Plymouth, is also deeply appreciated. This work was supported in part by NSF Grant OCE 77-23278 to the Cooperative Oceanographic Program of Duke University Marine Laboratory and a grant from Utica College.
REFERENCES BLANC F., P. CHARDY,A. LAUREC and J.-P. REYS (1976) Choix des metriques qualitatives en analyse d'inertie. Implications en 6cologie marine benthique. Marine Biology, 35, 49-67.
Carolina slope barrier
853
CUTLE~ E. B. (1973) Sipuncula of the western North Atlantic. Bulletin of the American Museum c~f Natural History, 142, 105-204. CUTLER E. B. (1975) Zoogeographical barrier on the continental slope offCape Lookout, North Carolina. DeepSea Research, 22, 893-901. SmUT M. (1979) Distribution and diversity of asteroids in Atlantic abyssal basins. AMBIO, in press.
APPENDIX
Modifications in species presence~absence data ( + , species present, O, species absent; numbers at bottom are degrees north latitude; Siboglinum holmei is removed) Species
Siboglinum ekmani Siboglinum pholidotum Siboglinum angustum Siboglinum longicollum Siboglinumfulgens Siboglinum gosnoldae Oligobrachiafloridana Nereilium species Lamellisabella species I Lamellisabella species II
Zones 1
2
3
4
5
6
7
8
9
10
11
+ +
+ O
+ +
+ +
+ +
+ +
+ +
+ +
+ +
+ O
+ +
12 + +
13 O O
14 + +
0 0 + 0 0 0 0 +
+ 0 + 0 0 0 0 0
+ 0 + 0 0 0 0 0
+ + + 0 + 0 + +
+ 0 + 0 0 0 0 0
+ 0 + 0 0 0 0 0
+ 0 + 0 0 0 0 0
+ 0 + 0 + + + 0
+ + + 0 + + + 0
+ 0 0 + + 0 + 0
+ + 0 0 + + + 0
+ + + 0 + + + 0
+ + 0 0 0 + © 0
+ + 0 0 0 0 + 0
0011-7471/79/0701-0851 $02.00/0
NOTE
North Carolina continental slope zoogeographical barrier EDWARD B. CUTLER* and KAREN DOBLE* (Received 3 October 1978 ; in revised.lbrm 12 February 1979, accepted 12 February 1979)
Abstract--Collections of sipunculans and pogonophorans from depths between 150 and 2000 m around latitude 35°30'N were analyzed and used to supplement earlier information from this region. The addition of eight pogonophoran species from this area and minor revisions of earlier data reaffirm and strengthen the hypothesis that a zoogeographical barrier for slope dwelling infauna exists around 34°N off Cape Lookout, North Carolina.
IN 1975 Cutler suggested that a zoogeographical barrier for benthic infaunal invertebrates exists on the continental slope off Cape Lookout, North Carolina (34°N). This was based on an analysis of Sipuncula and Pogonophora distribution patterns in the area between 31040 ' and 36°19'N latitude at depths between 150 and 2500 m. This region was divided into 14 equal zones of 20-min intervals, then, based on presence or absence data, similarity coefficients were calculated and a cluster analysis was performed. It was noted that, "The peculiar nature of Zone 12 (35°20 ' to 35°39'N) is probably the result of only six stations being occupied there, yielding no pogonophorans and only five species of sipunculans." It was peculiar in that it did not group with the rest of the cluster until a similarity level of 27. None of the stations in Zone 12 was deeper than 500 m. It was evident that an unfortunate gap existed in the data so when the opportunity for an additional collecting trip on the R/V Eastward became available in July 1977, we returned to this region. We occupied five stations near 35°30'N at approximately 200, 500, 1000, 1500, and 2000 m. At each depth two collections were made using the Day (Capetown) Dredge and the Small Biological Trawl (see CUTLER, 1973, for details on technique). This particular area of the continental slope just north of Cape Hatteras is quite steep between 200 and 1500 m with irregular ridges and valleys. Several hauls revealed fine, black, apparently anaerobic sediments. Three stations in Zone 13 (35°40 ' to 35°59'N) were also made at 1000, 1500, and 2000 m to verify earlier finds there. No previously unreported species were found in Zone 13, so this has no effect on the hypothesis except additional confirmation. From Zone 12, of the five previously reported sipunculans, three were collected this time. The important feature is that eight pogonophoran species were collected over the range of depths from this zone for the first time (Appendix). In addition to this new material, E. C. Southward's reconsideration of some earlier collections (personal communication) led to several revisions of the pogonophoran data matrix: the lamellisabellids were separated into two species (yet undescribed); an unnamed Nereilinum species was added; Siboglinum holmei was removed and changes were made in S. gosnoldi and S. fulgens. The appendix shows only those species modified since CUTLER (1975, Appendix A). * Biology Department, Utica College of Syracuse University, Utica, NY 13502, U.S.A. 851
852
EDWARD B, CUTLER and KAREN DOBLE
STATIONS south
north 14 13 12 11 9
8
10734
52
--85 .-80
,,-75 0
,.-70 .-65
--60
-.55
I ,-50
Fig. 1. Dendogram showing results of group average cluster analysis on Dice's similarity coefficients for 14 zones.
With these new data, the numerical analysis was rerun using Dice's similarity coefficient and the group average cluster analysis. The reasons for using this coefficient were discussed in CUTLER(1975). BLANC,CHARDY, LAURECand REYS (1976) discussed Dice's coefficient along with several others, including Kulczinski's. SIBUET (1979) has used the Kulczinski 2 Index for her analysis of asteroid distribution as she has a high degree of heterogeneity in the number of species present in each area. That is not the case in our data, so we used Dice's coefficient believing in its continued validity. Zone 12 now pairs with Zones 9 and 11 at a similarity level greater than 70, creating a much more symmetrical dendrogram (Fig. 1). This work removes an apparent anomaly and strengthens the hypothesis set forth in CUTLER(1975) of a zoogeographical barrier for slope dwelling sedentary infauna around 34°N (more southerly for shallower species and more northerly for deeper species), the probable cause being the effects of bottom currents on larval dispersion. Acknowledgements--We are indebted to the officers and crew of the R/V Eastward, a group of colleagues who assisted in the collections, and NORMA CUTLER, who helped in several phases including the preparation of this manuscript. The continued interest and assistance of E. C. SOUTHWARD, Plymouth, is also deeply appreciated. This work was supported in part by NSF Grant OCE 77-23278 to the Cooperative Oceanographic Program of Duke University Marine Laboratory and a grant from Utica College.
REFERENCES BLANC F., P. CHARDY,A. LAUREC and J.-P. REYS (1976) Choix des metriques qualitatives en analyse d'inertie. Implications en 6cologie marine benthique. Marine Biology, 35, 49-67.
Carolina slope barrier
853
CUTLE~ E. B. (1973) Sipuncula of the western North Atlantic. Bulletin of the American Museum c~f Natural History, 142, 105-204. CUTLER E. B. (1975) Zoogeographical barrier on the continental slope offCape Lookout, North Carolina. DeepSea Research, 22, 893-901. SmUT M. (1979) Distribution and diversity of asteroids in Atlantic abyssal basins. AMBIO, in press.
APPENDIX
Modifications in species presence~absence data ( + , species present, O, species absent; numbers at bottom are degrees north latitude; Siboglinum holmei is removed) Species
Siboglinum ekmani Siboglinum pholidotum Siboglinum angustum Siboglinum longicollum Siboglinumfulgens Siboglinum gosnoldae Oligobrachiafloridana Nereilium species Lamellisabella species I Lamellisabella species II
Zones 1
2
3
4
5
6
7
8
9
10
11
+ +
+ O
+ +
+ +
+ +
+ +
+ +
+ +
+ +
+ O
+ +
12 + +
13 O O
14 + +
0 0 + 0 0 0 0 +
+ 0 + 0 0 0 0 0
+ 0 + 0 0 0 0 0
+ + + 0 + 0 + +
+ 0 + 0 0 0 0 0
+ 0 + 0 0 0 0 0
+ 0 + 0 0 0 0 0
+ 0 + 0 + + + 0
+ + + 0 + + + 0
+ 0 0 + + 0 + 0
+ + 0 0 + + + 0
+ + + 0 + + + 0
+ + 0 0 0 + © 0
+ + 0 0 0 0 + 0