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CLIMATE CHANGE IN THE MID ATLANTIC BIGHT

Posted on: March 12, 2020

 

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THIS POST IS A CRITICAL REVIEW OF THE CLAIM THAT HUMAN FOSSIL FUEL EMISSIONS  HAVE ENDANGERED THE SURVIVAL OF THE COMMON WHELK (B undatum) IN THE MID ATLANTIC BIGHT BY WAY OF RISING OCEAN HEAT CONTENT IN THAT REGION CAUSED BY GLOBAL WARMING. SOURCE: “Borsetti, S., Munroe, D., Rudders, D. et al. Timing of the reproductive cycle of waved whelk, Buccinum undatum, on the U.S. Mid-Atlantic Bight. Helgol Mar Res 74, 5 (2020). https://doi.org/10.1186/s10152-020-00537-6” [LINK] 

 

THE POST IS PRESENTED IN THREE PARTS.

PART-1 IS A SUMMARY OF THE CLIMATE CHANGE CLAIMS MADE IN THE BORSETTI 2020 PAPER. PART-2 IS A SUMMARY OF THE BORSETTI 2017 SEASONAL CYCLE PAPER. PART-3 IS A CRITICAL COMMENTARY ON THE BORSETTI 2020 PAPER

THE MID ATLANTIC BIGHT REGIONbight

 

NORTH ATLANTIC SHELF TEMPERATURE SEASONAL CYCLE

 

 

PART-1: THE BORSETTI 2020 AGW CLIMATE CHANGE PAPER

  1. Climate change could threaten the survival and development of common whelk—a type of sea snail—in the mid-Atlantic region, according to a study led by scientists at Rutgers University-New Brunswick. The common, or waved, whelk (B undatum) is an important commercial species that has been harvested for decades in Europe and Canada for bait and human consumption. Its habitat within the mid-Atlantic region is one of the Earth’s fastest warming marine areas and annual fluctuations in the bottom temperature are among the most extreme on the planet due to unique oceanographic conditions.
  2. Climate change will result in higher temperatures and that’s a problem because temperatures are closely linked to the whelk’s spawning cycle and temperature increases could threaten its survival. This is the first time the species’ annual reproductive cycle in the mid-Atlantic has been documented.  Previous studies showed that the common whelk, a cold-water species, has some resilience to warmer temperatures but rising temperatures may have a negative impact on whelk survival, recruitment, development and growth.
  3. Commercial fishermen are interested in developing a fishery for this species in the mid-Atlantic. Whelk fisheries have expanded in many countries, resulting in a global increase in whelk landings over the last 20 years. But whelk have highly variable traits, such as reproductive timing, that need to be studied before intense fishing begins because the species is vulnerable to over-exploitation and that could happen if fishery managers assume populations are uniform throughout its habitat.
  4. The resilience of whelk comes with a trade-off: fewer offspring, which can negatively impact the whelk population and fisheries landings. Previous research examined traits such as the size whelk reach in maturity, sex ratio and abundance. For the study on whelk reproduction, the team caught 602 whelk off the coast from Cape May County to the Delmarva Peninsula from January 2017 to September 2017. The study examined fluctuations in whelk body metrics, gonad weights and sea-bottom temperatures.

 

 

PART-2: THE BORSETTI  2017 SEASONAL CYCLE PAPER

  1. (FROM THE ABSTRACT) Maturation and reproduction timing vary by location for this species and are likely linked to bottom water temperature. This study examined the seasonal fluctuations in relevant body metrics and gonadosomatic index (relating to reproduction) in relation to bottom temperature to assess the timing of the reproductive cycle of the B. undatum population in the southern-most extent of this species’ range in the Atlantic. To characterize variation over the maturation schedule, nine locations in the Mid-Atlantic Bight (MAB) were sampled five times between January 2017 and September 2017. Maturity was assessed macroscopically, with morphological methods, and via gonadosomatic indices. Male behavioral maturity estimates, based on a penis length to shell length index (PL50), were compared to estimates made using other methods for assessing maturity to test the efficacy of this commonly used ratio. Mature whelk were found in all months and peak reproductive activity was observed in spring and early summer. This timing suggests that ideal sampling to visually identify maturity to estimate size of maturity would be late winter or early spring. Unique oceanographic dynamics in the MAB, such as strong seasonal stratification results in large changes in annual bottom temperature which appears to be closely linked to the reproductive cycle in this region. {Note: The MAB is a non-stationary boundary between cool Arctic and tropical waters with seasonal dynamics that are important variables for shellfish habitats} Our data suggest that B. undatum in the MAB experience spawning and development at ~ 7–8 °C; temperatures warmer than Canadian populations and cooler than some UK populations.
  2. (TEMPERATURE DATA): Ocean temperature 1980–2015 was provided by the Regional Ocean Modeling System (ROMS) Earth Systems Model. This modelling temperature time series was bias-corrected using observed bottom water temperatures measured in spring, summer, and fall during the annual minimum and maximum bottom temperatures. These simulated data formed the basis for the generation of a 10-year, monthly climatology from 2005 to 2015 for the southern MAB region that was then used to examine the relationship between temperature and the reproductive cycle of whelk in the MAB.  {Note: ROMS is a climate model that estimates ocean temperature with the Earth System Model}. More info at myroms.org [LINK]
  3. (FINDINGS)  There an interest in developing a commercial fishery industry for B. undatum in the MAB and an understanding of its population dynamics is important for that development. Early spring is an appropriate time to assess sexual maturity (i.e. penis length) in the MAB. The relationship of the reproductive cycle with bottom water temperature is important in this regard.  Further study is needed for an understanding of interannual variability including for example in population growth, connectivity, and ecosystem interaction.

 

 

PART 3: CRITICAL COMMENTARY

  1. The AGW climate change impact on the reproduction of B-undatum is based on the observed seasonal cycle in reproduction that peaks during low seasonal bottoms temperature in March and is lower in the seasonally warmer bottoms temperature of September. These data on seasonal temperature and breeding cycles are then arbitrarily interpreted as a causal relationship between the two cycles without any evidence or lab tests to establish an empirical basis for that causation. Without direct evidence of a causation relationship between temperature and breeding, this conclusion is a theory of convenience without an empirical basis. Although there is a seasonal temperature cycle and there is also a seasonal breeding cycle, it cannot be assumed on this basis alone that the two seasonal cycles are causally related such that one drives the other.
  2. Consider for example, that most oceanic bottom  dwellers have a breeding seasonal cycle in an environment that has no seasonal temperature cycle {R. Y. GEORGE & R. J. MENZIES, “Further Evidence for Seasonal Breeding Cycles in Deep Sea” Nature volume 220, pages80–81(1968)}. In general, the deep sea floor has no temperature seasonal cycle and yet creatures down there do have breeding seasonal cycles. There is no evidence that all breeding seasonal cycles are driven by temperature seasonal cycles.
  3. Yet another faux deduction from seasonal cycles in this research is that the steep seasonal temperature cycle implies that the region is particularly sensitive to AGW warming and that therefore we should expect a steeper than average temperature response in shelf bottom temperatures to AGW forcing of surface temperature. This interpretation of the seasonal temperature cycle has no basis.
  4. Conclusion: The 2020 paper appears to be a derived from the idea that the author’s 2017 seasonal cycle paper can somehow be extended into a climate change paper. However, as we have argued above, the seasonal cycles in temperature and breeding cannot be interpreted either as a causal relationship between the temperature and breeding or in terms of an exaggerated AGW impact on shelf bottom temperature simply because it has a steep temperature seasonal cycle. The AGW climate change findings of the 2020 paper of an impact of climate change on breeding are rejected on this basis. 

 

FOOTNOTE: THE WIDELY HELD BELIEF IN CLIMATE SCIENCE THAT CARBON DIOXIDE AND GLOBAL WARMING ARE BAD FOR CRUSTACEANS IS INCONSISTENT WITH A PREFERENCE FOR HYDROTHERMAL VENTS BY DEEP OCEAN CRUSTACEANS. 

 

 

 

 

 

 

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