Vol. 62, 2023

(update: 2023.8.11)

Organismal Responses to Coastal Acidification Informed by Interrelating Erosion, Roundness and Growth of Gastropod Shells

David J. Marshall^1,* and Amira Rashid²

¹Environmental and Life Sciences, Faculty of Science, Jalan Tungku Link, Gadong, Universiti Brunei Darussalam, Brunei Darussalam, BE1410. *Correspondence: E-mail: davidmarshall11@gmail.com (Marshall). Tel: +673 246 0923 ext 1379.
²Environmental and Life Sciences, Faculty of Science, Universiti Brunei Darussalam, Brunei Darussalam. E-mail: mira_605@hotmail.com (Rashid)

(Received 29 December 2022 / Accepted 19 June 2023 / Published 11 August  2023)
Communicated by Benny K.K. Chan

Current understanding of how calcifying organisms respond to externally forced oceanic and coastal acidification (OCA) is largely based on short-term, controlled laboratory or mesocosm experiments. Studies on organismal responses to acidification (reduced carbonate saturation and pH) in the wild, where animals simultaneously interact with a range of biotic and abiotic circumstances, are limited in scope and interpretation. The present study aimed to better understand how gastropod shell attributes and their interrelations can inform about responses to coastal acidification. We investigated shell chemical erosion, shell roundness, and growth rate of Planaxis sulcatus snails, which are locally exposed to acidified and non-acidified rocky intertidal water. We tested a new approach to quantifying shell erosion based on the spiral suture length (EI, erosion index) and found that shell erosion mirrored field acidification conditions. Exposure to acidification caused shells to become rounder (width/length). Field growth rate, determined from apertural margin extension of marked and later recaptured snails, was strongly negatively related to both shell erosion and shell roundness. Since different shell attributes are indicative of different relationships—shell erosion is an extrinsic passive marker of acidification, and shell roundness and growth rate are intrinsic performance responders—analyzing their interrelations can imply causation, enhance predictive power, and bolster interpretation confidence. This study contributes to the methodology and interpretation of findings of trait-based field investigations to understand organismal responses to coastal acidification.

Key words: Biomonitoring, Growth rate, Indicators, Ocean acidification, Snails, Shell dissolution, Shell shape

Citation: Marshcall DJ, Rashid A. 2023. Organismal responses to coastal acidification informed by interrelating erosion, roundness and growth of gastropod shells. Zool Stud 62:41. doi:10.6620/ZS.2023.62-41.

Supplementary materials: Fig. S1