• Anti-predation strategy, growth rate and extinction amongst Pliocene scallops of the US eastern seaboard

      Johnson, Andrew L. A.; Valentine, Annemarie; Leng, Melanie J.; Sloane, Hilary J.; Schoene, Bernd; Surge, Donna; University of Derby; University of Loughborough; British Geological Survey; University of Mainz; et al. (2017-06-29)
      Placopecten, Chesapecten and Carolinapecten are scallop genera occurring in the Pliocene of the US eastern seaboard. The first (extant) is a smooth, streamlined form, adept at escaping predators by swimming (‘flight’ strategy). The other two (extinct) are plicate forms. Plication facilitates a ‘resistance’ strategy towards predators which is benefited by large size and high shell thickness - maximally so if these states are achieved early in life. Oxygen isotope profiles show that in early ontogeny, Pliocene Placopecten grew at the same moderate rate as modern Placopecten. By contrast, Chesapecten grew as fast as the fastest-growing modern scallop and developed an unusually thick shell, while Carolinapecten grew substantially faster still, this probably enabled by high primary productivity. Extinction of these genera, and survival of Placopecten, can be attributed to a decline in productivity which prevented a maximally effective ‘resistance’ strategy towards predators but had no deleterious impact on a ‘flight’ strategy.
    • Anti-predation strategy, growth rate and extinction amongst Pliocene scallops of the US eastern seaboard

      Johnson, Andrew L. A.; Valentine, Annemarie; Leng, Melanie J.; Sloane, Hilary J.; Schoene, Bernd; Surge, Donna; University of Derby; University of Loughborough; British Geological Survey; University of Mainz; et al. (2017-07-07)
      Placopecten, Chesapecten and Carolinapecten are scallop (pectinid bivalve) genera occurring in the Pliocene of the US eastern seaboard. The first, present in the area today, is a smooth, streamlined form, adept at escaping predators by swimming (‘flight’ strategy). The other two, which are extinct, are plicate (‘ribbed’) forms. Plication facilitates a ‘resistance’ strategy towards predators which is benefited by large size and high shell thickness - maximally so if these states are achieved early in life. Oxygen isotope (δ18O) profiles show that early ontogenetic extensional growth in Pliocene Placopecten was at the same moderate rate as in modern Placopecten. By contrast, in Chesapecten it was as fast as in the fastest-growing modern scallop (c. 80 mm/annum), and accompanied by development of an unusually thick shell, while in Carolinapecten it was substantially faster still (<140 mm/annum). Rapid growth in Chesapecten and Carolinapecten may have been enabled by high primary productivity, which is indicated by the abundance, diversity and large size of co-occurring vertebrates. The extinction of Chesapecten and Carolinapecten, and the survival of Placopecten, can be attributed to a decline in primary productivity which prevented a maximally effective ‘resistance’ strategy towards predators but had no deleterious impact on a ‘flight’ strategy.
    • Anti-predation strategy, growth rate and extinction amongst Pliocene scallops of the US eastern seaboard

      Johnson, Andrew L. A.; Valentine, Annemarie; Leng, Melanie J.; Sloane, Hilary J.; Schöne, Bernd R.; Surge, Donna; University of Derby; University of Loughborough; British Geological Survey; University of Mainz; et al. (European Geosciences Union, 2017-04-28)
      Placopecten, Chesapecten and Carolinapecten are scallop (pectinid bivalve) genera occurring in the Pliocene of the US eastern seaboard. The first, present in the area today, is a smooth, streamlined form, adept at escaping predators by swimming (‘flight’ strategy). The other two, which are extinct, are plicate (‘ribbed’) forms. Plication facilitates a ‘resistance’ strategy towards predators which is benefited by large size and high shell thickness - maximally so if these states are achieved early in life. Oxygen isotope profiles show that early ontogenetic extensional growth in Pliocene Placopecten was at the same moderate rate as in modern Placopecten. By contrast, in Chesapecten it was as fast as in the fastest-growing modern scallop (c. 80 mm/annum), and accompanied by development of an unusually thick shell, while in Carolinapecten it was substantially faster still (<150 mm/annum). Rapid growth in Chesapecten and Carolinapecten was probably enabled by high primary productivity, for which there is evidence from sediment composition and the associated biota. The extinction of Chesapecten and Carolinapecten, and the survival of Placopecten, can be attributed to a decline in primary productivity which prevented a maximally effective ‘resistance’ strategy towards predators but had no deleterious impact on a ‘flight’ strategy.
    • The cause of late Cenozoic mass extinction in the western Atlantic: insights from sclerochronology

      Johnson, Andrew L. A.; Valentine, Annemarie; Leng, Melanie J.; Surge, Donna; Williams, Mark; University of Derby (The Palaeontological Association, 2014-12)
      Heavy late Cenozoic extinction amongst marine molluscs in the western Atlantic has traditionally been interpreted as a consequence of climatic deterioration. However, the pattern of extinction was not the same in the eastern Atlantic, where conditions also became colder. A fall in primary productivity, suggested by a decline in phosphate deposition, may be the real explanation for western Atlantic extinctions. Evidence in support comes from isotopic- and increment-based (sclerochronological) indications of growth rate in Pliocene scallops. A western Atlantic genus that has survived to the present (Placopecten) had the same moderate growth rate in the Pliocene as now, while two genera that became extinct (Carolinapecten and Chesapecten) had growth rates as fast as any known amongst living scallops. Such rapid growth implies abundant food. Selective extinction of a fast-growing species has also been documented amongst Pliocene oysters in the Caribbean region and attributed to a decline in primary productivity. The likely cause of this is the development of the Central American Isthmus and the consequent reorganization of oceanic circulation in the Gulf of Mexico and wider North Atlantic.
    • Environment and extinction in the late Cenozoic of the North Atlantic area - insights from sclerochronology

      Johnson, Andrew L. A.; University of Derby (2017-10-12)
      Sclerochronology is the sister-field of dendrochronology, the study of tree rings. It involves analysis of the size and composition of increments within mineralised skeletons formed by accretion, such as those of bivalve molluscs, corals and coralline algae. Detailed information can be obtained on the age, growth-rate and environment of the organism concerned. In this talk I will show how sclerochronology is providing insights into Plio-Pleistocene changes in marine productivity and temperature in the North Atlantic region: their nature, cause and possible links to bivalve mass extinction during this interval (45% and 65% loss of species in the eastern and western Atlantic, respectively). This information may inform prediction of future extinction associated with global warming.
    • Evidence, cause and consequence of exceptionally rapid growth in Pliocene scallops of the US eastern seaboard

      Johnson, Andrew L. A.; Valentine, Annemarie; Leng, Melanie J.; Sloane, Hilary J.; Schoene, Bernd; Surge, Donna; University of Derby (4th International Sclerochronology Conference, 2016-06)
      Scallops are amongst the fastest growing of bivalves, with many species growing in the order of 40 mm per annum in early ontogeny, and reliable evidence of early ontogenetic growth-rates up to 70 mm per annum in wild populations of certain species. From the evidence of oxygen isotope (δ18O) sclerochronology, modern examples of the western Atlantic genus Placopecten grow about 40 mm per annum in early ontogeny. The same approach reveals similar growth rates in Pliocene examples from Virginia and North Carolina. By contrast Pliocene examples of the extinct genera Chesapecten and Carolinapecten from Virginia grew at least 75 mm per annum, faster than has been recorded in any wild modern scallop, and examples of Carolinapecten from Florida grew up to 140 mm per annum, twice the maximum rate in wild modern scallops. The rapid overall growth of Carolinapecten is matched by exceptionally large microgrowth increments. In specimens with the fastest overall growth the number of increments approximately equals the number of days indicated by the oxygen isotopic data (e.g. c. 180 over half an oxygen isotope cycle), implying that deposition was daily. Specimens with slower overall growth do not have smaller increments but have substantially fewer than the number of days indicated by δ18O evidence, showing that reduced overall growth was a consequence of periodic interruptions rather than permanently less favourable conditions. Since few individuals lived more than a year, rapid somatic growth must have been accompanied by gamete production, implying abundant food resources. Intervals of particularly rapid growth (largest microgrowth increments) are fairly closely correlated with increases in δ13C, as might have been caused by phytoplankton blooms. However, there is little evidence that these were stimulated by upwelling since there are few indications of a matching increase in δ18O (i.e. colder water). Instead, primary productivity may have been enhanced by nutrient supply from the land. Whatever the cause of high primary productivity in the Pliocene of the US eastern seaboard, the subsequent demise of two scallop genera with exceptionally rapid growth seems as likely to relate to a decline in productivity as to a fall in temperature.
    • Growth rate and extinction amongst Plio-Pleistocene bivalve molluscs of the western and eastern North Atlantic region

      Clarke, Abigail; Featherstone, Aaron; Heywood, Daniel; Thornton, Luke; Richardson, Kathryn; Johnson, Andrew L. A.; University of Derby (2017-07-03)
    • Growth rate, extinction and survival amongst late Cenozoic bivalves of the North Atlantic

      Johnson, Andrew L. A.; Harper, Elizabeth M.; Clarke, Abigail; Featherstone, Aaron C.; Heywood, Daniel J.; Richardson, Kathryn E.; Spink, Jack O.; Thornton, Luke A.H.; University of Derby (Taylor & Francis, 2019-09-12)
      Late Cenozoic bivalve extinction in the North Atlantic and adjacent areas has been attributed to environmental change (declines in temperature and primary production). Within scallops and oysters—bivalve groups with a high growth rate—certain taxa which grew exceptionally fast became extinct, while others which grew slower survived. The taxa which grew exceptionally fast would have obtained protection from predators thereby, so their extinction may have been due to the detrimental effect of environmental change on growth rate and ability to avoid predation, rather than environmental change per se. We investigated some glycymeridid and carditid bivalves—groups with a much lower growth rate than scallops and oysters—to see whether extinct forms from the late Cenozoic of the North Atlantic grew faster than extant forms, and hence whether their extinction may also have been mediated by increased mortality due to predation. Growth rate was determined from the cumulative width of annual increments in the hinge area; measurements were scaled up to overall shell size for the purposes of comparison with data from living species. Growth of the extinct glycymeridid Glycymeris subovata was at about the same rate as the slowest-growing living glycymeridid and much slower than in late Cenozoic samples of extant G. americana, in which growth was at about the same rate as the fastest-growing living glycymeridid. Growth of extinct G. obovata was also slower than G. americana, and that of the extinct carditid Cardites squamulosa ampla similarly slow (evidently slower than in the one living carditid species for which data are available). These findings indicate that within bivalve groups whose growth is much slower than scallops and oysters, extinction or survival of taxa through the late Cenozoic was not influenced by whether they were relatively fast or slow growers. By implication, environmental change acted directly to cause extinctions in slow-growing groups, rather than by increasing susceptibility to predation.
    • Isotopic temperatures from the early and mid-pliocene of the US Middle Atlantic coastal plain, and their implications for the cause of regional marine climate change

      Johnson, Andrew L. A.; Valentine, Annemarie; Leng, Melanie J.; Sloane, Hilary J.; Schöne, Bernd R.; Balson, Peter S.; University of Derby; University of Loughborough; British Geological Survey; University of Mainz (Society for Sedimentary Geology (SEPM), 2017-04-18)
      Mean seasonal extreme temperatures on the seafloor calculated from the shell δ18O of the scallop Placopecten clintonius from the basal part of the early Pliocene Sunken Meadow Member (Yorktown Formation) in Virginia are very similar to those from the same horizon at the latitude of Cape Hatteras in North Carolina (~210 km to the south). The lowest and highest temperatures calculated from each shell (using δ18Oseawater = +0.7‰) give mean values for winter and summer of 8.4 ± 1.1 °C (± 1σ) and 18.2 ± 0.6 °C in Virginia, and 8.6 ± 0.4 °C and 16.5 ± 1.1 °C in North Carolina (respective median temperatures: 13.3 °C and 12.6 °C). Patterns of ontogenetic variation in δ18O, δ13C and microgrowth increment size indicate summer water-column stratification in both areas, with summer surface temperatures perhaps 6 °C higher than on the seafloor. The low winter paleotemperatures in both areas are most simply explained by the greater southward penetration of cool northern waters in the absence of a feature equivalent to Cape Hatteras. The same current configuration but a warmer general climate can account for the high benthic seasonal range (over 15.0 °C in some cases) but warmer median temperatures (15.7-21.3 °C) derived from existing δ18O data from scallops of the higher Yorktown Formation (using δ18Oseawater = +0.7‰ for the upper Sunken Meadow Member and δ18Oseawater = +1.1‰ for the mid-Pliocene Rushmere, Morgarts Beach and Moore House members). Existing δ18O data from the infaunal bivalve Mercenaria of the Rushmere Member yields a similarly high median temperature (21.6 °C) but a low seasonal range (9.2 °C), pointing to the periodic influence of warm currents, possibly at times when the Gulf Stream was exceptionally vigorous.
    • Life history, environment and extinction of the scallop Carolinapecten eboreus (Conrad) in the Plio-Pleistocene of the U.S. eastern seaboard.

      Johnson, Andrew L. A.; Valentine, Annemarie M.; Leng, Melanie J.; Schöne, Bernd R.; Sloane, Hilary J.; University of Derby; Nottingham Trent University; British Geological Survey; University of Mainz (SEPM (Society for Sedimentary Geology), 2019-02-01)
      Plio-Pleistocene mass extinction of marine bivalves on the U.S. eastern seaboard has been attributed to declines in temperature and primary production. We investigate the relationship of growth rate in the scallop Carolinapecten eboreus to variation in these parameters to determine which contributed to its extinction. We use ontogenetic profiles of shell d18O to estimate growth rate and seasonal temperature, microgrowth-increment data to validate d18O-based figures for growth rate, and shell d13C to supplement assemblage evidence of production. Postlarval growth started in the spring/summer in individuals from the Middle Atlantic Coastal Plain but in the autumn/winter in some from the Gulf Coastal Plain. Growth rate typically declined with age and was usually higher in summer than winter. Many individuals died in winter but the largest forms typically died in spring, possibly on spawning for the first time. No individuals lived longer than two years and some grew exceedingly fast overall, up to 60% more rapidly than any other scallop species (, 145.7 mm in a year). Faster growth was generally achieved by secreting more rather than larger microgrowth increments. Some very fast-growing individuals lived in settings of high production and low temperature. No individuals grew slowly under high production whereas most if not all grew slowly under ‘average’ production and low temperature. In that the rapid growth evidently enabled by high production would have afforded protection from predators, Plio-Pleistocene decline in production was probably contributory to the extinction of C. eboreus. However, the negative impact of low temperature on growth under ‘average’ production suggests that temperature decline played some part.
    • Marine climate and hydrography of the Coralline Crag (early Pliocene, UK): isotopic evidence from 16 benthic invertebrate taxa.

      Vignols, Rebecca M.; Valentine, Annemarie M.; Finlayson, Alana G.; Harper, Elizabeth M.; Schöne, Bernd R.; Leng, Melanie J.; Sloane, Hilary J.; Johnson, Andrew L. A.; University of Derby; University of Cambridge; et al. (Elsevier, 2018-05-24)
      The taxonomic composition of the biota of the Coralline Crag Formation (early Pliocene, eastern England) provides conflicting evidence of seawater temperature during deposition, some taxa indicating cool temperate conditions by analogy with modern representatives or relatives, others warm temperate to subtropical/tropical conditions. Previous isotopic (δ18O) evidence of seasonal seafloor temperatures from serial ontogenetic sampling of bivalve mollusk shells indicated cool temperate winter (< 10 °C) and/or summer (< 20 °C) conditions but was limited to nine profiles from two species, one ranging into and one occurring exclusively in cool temperate settings at present. We supplement these results with six further profiles from the species concerned and supply seven more from three other taxa (two supposedly indicative of warm waters) to provide an expanded and more balanced database. We also supply isotopic temperature estimates from 81 spot and whole-shell samples from these five taxa and 11 others, encompassing ‘warm’, ‘cool’ and ‘eurythermal’ forms by analogy with modern representatives or relatives. Preservation tests show no shell alteration. Subject to reasonable assumptions about water δ18O, the shell δ18O data either strongly indicate or are at least consistent with cool temperate seafloor conditions. The subtropical/tropical conditions suggested by the presence of the bryozoan Metrarabdotos did not exist. Microgrowth-increment and δ13C evidence indicate summer water-column stratification during deposition of the Ramsholt Member, unlike in the adjacent southern North Sea at present (well mixed due to shallow depth and strong tidal currents). Summer maximum surface temperature was probably about 5 °C above seafloor temperature and thus often slightly higher than now (17–19 °C rather than 16–17 °C), but only sometimes in the warm temperate range. Winter minimum surface temperature was below 10 °C and possibly the same as at present (6–7 °C). An expanded surface temperature range compared to now may reflect withdrawal of oceanic heat supply in conjunction with higher global temperature.
    • Seasonally resolved isotopic temperature data as a tool for identifying the cause of marine climate change in the Pliocene

      Johnson, Andrew L. A.; Valentine, Annemarie; Leng, Melanie J.; Sloane, Hilary J.; Schoene, Bernd; Surge, Donna; University of Derby; University of Loughborough; British Geological Survey; University of Mainz; et al. (2017-07-07)
      Alteration in the pattern and vigour of ocean currents has often been invoked as the principal driver of changes in regional climate, including cases in the recent past (Pliocene, Pleistocene and Holocene) and instances predicted in the near future. The theory behind such interpretations is, however, suspect (e.g. Crowley, 1996; Seager et al., 2002), and it may be that other regional or global drivers are more important. The present cool temperate marine climate on the US eastern seaboard north of Cape Hatteras (northernmost North Carolina and Virginia) reflects the influence of cool southward-flowing currents, and a similar influence can be inferred in the Early Pliocene (Johnson et al., 2017). Change to a warm temperate (or marginally subtropical) marine climate in the Late Pliocene has been ascribed to the impingement on the area of warm, northward-flowing currents, assisted by the absence of a barrier equivalent to Cape Hatteras (e.g. Williams et al., 2009). Seasonally resolved oxygen isotope (δ18O) data from bivalve shells reveals, however, that seasonal temperature range was often in excess of that characteristic of the area south of Cape Hatteras (influenced by warm currents), and indicates the continuing influence of cold currents from the north (Johnson et al., 2017). Some isotopic evidence of seasonal temperature range from bivalves is consistent with warm-current influence (Winkelstern et al., 2013), but otherwise the evidence points to a different control (probably global climatic change) on the Late Pliocene warming of marine climate on the US eastern seaboard that is shown by isotopic data for annual average temperature. References: Crowley, T.J. (1996) Pliocene climates: The nature of the problem. Marine Micropaleontology, 27, 3-12. Johnson, A.L.A., Valentine, A., Leng, M.J., Sloane, H.J., Schöne, B.R., Balson, P.S. (2017) Isotopic temperatures from the Early and Mid-Pliocene of the US Middle Atlantic Coastal Plain, and their implications for the cause of regional marine climate change. PALAIOS, 32, 250-269. Seager, R., Battisti, D.S., Yin, J., Gordon, N., Naik, N.H., Clement, A.C., Cane, M.A. (2002) Is the Gulf Stream responsible for Europe's mild winters? Quarterly Journal of the Royal Meteorological Society, 128, 2563-2586. Williams, M., Haywood, A.M., Harper, E.M., Johnson, A.L.A., Knowles, T., Leng, M.J., Lunt, D.J., Okamura, B., Taylor, P.D., Zalaziewicz, J. (2009) Pliocene climate and seasonality in North Atlantic shelf seas. Philosophical Transactions of the Royal Society of London, Series A, 367, 85–108. Winkelstern, I., Surge, D., Hudley, J.W. (2013) Multiproxy sclerochronological evidence for Plio-Pleistocene regional warmth: United States Mid-Atlantic Coastal Plain. PALAIOS, 28, 649-660.
    • Stable isotope (δ18O and δ13C) sclerochronology of Callovian (Middle Jurassic) bivalves (Gryphaea (Bilobissa) dilobotes) and belemnites (Cylindroteuthis puzosiana) from the Peterborough Member of the Oxford Clay Formation (Cambridgeshire, England): Evidence of palaeoclimate, water depth and belemnite behaviour

      Mettam, Colin; Johnson, Andrew L. A.; Nunn, Elizabeth V.; Schöne, Bernd R.; University of Derby (Elsevier, 2014-01-25)
      Incremental δ18O and δ13C signals were obtained from three well-preserved specimens of Cylindroteuthis puzosiana and from three well-preserved specimens of Gryphaea (Bilobissa) dilobotes from the Peterborough Member of the Oxford Clay Formation (Cambridgeshire, England). Through-ontogeny (sclerochronological) δ18O data from G. (B.) dilobotes appear to faithfully record seasonal temperature variations in benthic Callovian waters of the study area, which range from c. 14 °C to c. 17 °C (arithmetic mean temperature c. 15 °C). Water depth is estimated to have been in the region of c. 50 m, based upon comparisons between these data, previously published non-incremental sea surface δ18O values, and a modern analogue situation. Productivity in Callovian waters was comparable with that in modern seas, based upon δ13C data from G. (B.)dilobotes, with 13C depletion occurring during warmer periods, possibly related to an interaction between plankton blooms and intra-annual variations in mixing across a thermocline. Incremental δ18O data from C.puzosiana provide temperature minima of c.11 °C for all specimens but with maxima varying between c.14 °C and c.16 °C for different individuals (arithmetic mean values c. 13 °C). Temperatures for late ontogeny, when the C. puzosiana individuals must have been living close to the study site and hence the analysed specimens of G. (B.) dilobotes, are closely comparable to those indicated by the latter. However, for significant portions of ontogeny C. puzosiana experienced temperatures between c. 2 °C and c. 3 °C cooler than the winter minimum as recorded by co-occurring G. (B.) dilobotes. Comparisons with modern seas suggest that descent to a depth of c. 1000 m would be necessary to explain such cool minimum temperatures. This can be discounted due to the lack of deep waters locally and due to estimates of the depth tolerance of belemnites. The most likely cause of cool δ18O signals from C. puzosiana is a cosmopolitan lifestyle including migration to more northerly latitudes. Mean δ13C values from C. puzosiana are comparable with those from G.(B.)dilobotes. However, the incrementally acquired data are highly variable and probably influenced by metabolic effects.The probable identification of migratory behaviour in C. puzosiana calls into question the reliability of some belemnite species as place-specific palaeoenvironmental archives and highlights the benefits of adopting a sclerochronological approach.
    • The use of seasonally resolved temperature data to identify the cause of marine climate change

      Johnson, Andrew L. A.; Valentine, Annemarie; Leng, Melanie J.; Sloane, Hilary J.; Schöne, Bernd R.; Surge, Donna; University of Derby; University of Loughborough; British Geological Survey; University of Mainz; et al. (European Geosciences Union, 2017-04)
      On the continental shelf of the eastern USA, seasonal variation in water temperature is much lower south of Cape Hatteras than it is to the north as a result of the influence of warm currents, which raise winter temperature. High temperatures north of Cape Hatteras during the Pliocene have been attributed to greater northward penetration of warm currents in the absence of a feature analogous to Cape Hatteras. However, oxygen isotope thermometry using serial ontogenetic samples from scallops reveals a high seasonal temperature range at some horizons, suggesting that overall warming was the consequence of general climate change, with the absence of a ‘Cape Hatteras’ feature allowing greater southward penetration of cold currents, resulting in low winter temperatures at a southerly latitude. Evidence from other taxa indicates that at times seasonal variation in water temperature was quite low and that there was greater northward penetration of warm currents. This may relate to increases in vigour of the Gulf Stream. The study shows how seasonally resolved temperature data can assist identification of the driving forces of marine climate change.