Estimates of critical upper maxima (CTmax) of kelp species are strongly influenced by biogeography and thermal history.

Estimates of critical upper maxima (CTmax) of kelp species are strongly influenced by biogeography and thermal history. | Authorea try { document.documentElement.classList.add('js'); } catch (e) { } var _gaq = _gaq || []; _gaq.push(['_setAccount', 'G-8VDV14Y67G']); _gaq.push(['_trackPageview']); (function() { var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true; ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s); })(); Skip to main content Preprints Collections Wiley Open Research IET Open Research Ecological Society of Japan All Collections About About Authorea FAQs Contact Us Quick Search anywhere Search for preprint articles, keywords, etc. Search Search ADVANCED SEARCH SCROLL Ecology and Evolution This is a preprint and has not been peer reviewed. Data may be preliminary. 12 May 2026 V1 Latest version Share on Estimates of critical upper maxima (CTmax) of kelp species are strongly influenced by biogeography and thermal history. Authors : Tayla Leathers 0009-0000-2055-3081 [email protected] , Dan Smale 0000-0003-4157-541X [email protected] , and Nathan King [email protected] Authors Info & Affiliations https://doi.org/10.22541/authorea.15003032/v1 44 views 17 downloads Contents Abstract Supplementary Material Information & Authors Metrics & Citations View Options References Figures Tables Media Share Abstract Experimentally derived critical thermal maxima values (CTmax) are widely used to estimate species’ thermal tolerances and, increasingly, to predict their vulnerability to chronic warming and heatwaves. However, accumulating evidence from model taxa such as fish and insects suggests that CTmax is dynamic and sensitive to multiple environmental and methodological factors, potentially limiting its application as a fixed species level metric. Here, we quantified CTmax in three habitat‑forming kelp species (Laminaria digitata, Saccharina latissima and Laminaria ochroleuca) that occupy contrasting positions of their biogeographic range in the Western English Channel (northeast Atlantic). We assessed how methodological approach (whole plants vs excised meristematic discs) and thermal history across multiple timescales (seasonal climatology and acute marine heatwaves, MHWs) shape upper thermal limits. Meristematic discs provided CTmax estimates comparable to whole plants in the two cool‑water species (L. digitata and S. latissima), but significantly underestimated whole‑plant tolerance in the warm‑affinity species (L. ochroleuca). This divergence most likely reflected species-specific biology with L. ochroleuca relying more strongly on whole‑organism integration and internal storage to maintain high thermal performance. Seasonal climatology influenced CTmax in both cool water species, with pronounced declines in autumn relative to spring and summer, consistent with narrower thermal safety margins and cumulative stress accrued over summer. Exposure to an extreme simulated MHW caused substantial reductions in CTmax across all species, with the largest decline (> 7 °C) observed in L. ochroleuca. Together, these results show that CTmax is highly plastic, shaped by species’ biological traits, methodological approach and thermal history. Treating CTmax as a fixed trait risks misrepresenting population-level vulnerability of habitat-forming kelp species and, most likely, other marine ectotherms. Incorporating thermal history and organismal biology into thermal‑tolerance assessments will improve predictions of the resilience of kelp species, and the ecosystems they underpin, under future ocean warming. Supplementary Material File (leathers et al 2026_sup.docx) leathers et al 2026_sup Download 36.19 KB Information & Authors Information Version history V1 Version 1 12 May 2026 Collection Ecology and Evolution Authors Affiliations Tayla Leathers 0009-0000-2055-3081 [email protected] The Marine Biological Association, Plymouth, United Kingdom of Great Britain and Northern Ireland, PL1 2PB View all articles by this author Dan Smale 0000-0003-4157-541X [email protected] The Marine Biological Association, Plymouth, United Kingdom of Great Britain and Northern Ireland, PL1 2PB View all articles by this author Nathan King [email protected] The Marine Biological Association, Plymouth, United Kingdom of Great Britain and Northern Ireland, PL1 2PB View all articles by this author Metrics & Citations Metrics Article Usage 44 views 17 downloads .FvxKWukQNSOunydq8rnd { width: 100px; } Citations Download citation Tayla Leathers, Dan Smale, Nathan King. Estimates of critical upper maxima (CTmax) of kelp species are strongly influenced by biogeography and thermal history.. Authorea . 12 May 2026. DOI: https://doi.org/10.22541/authorea.15003032/v1 If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download. For more information or tips please see 'Downloading to a citation manager' in the Help menu . Format Please select one from the list RIS (ProCite, Reference Manager) EndNote BibTex Medlars RefWorks Direct import Tips for downloading citations document.getElementById('citMgrHelpLink').addEventListener('click', function() { popupHelp(this.href); return false; }); $(".js__slcInclude").on("change", function(e){ if ($(this).val() == 'refworks') $('#direct').prop("checked", false); $('#direct').prop("disabled", ($(this).val() == 'refworks')); }); View Options View options PDF View PDF Figures Tables Media Share Share Share article link Copy Link Copied! Copying failed. Share Facebook X (formerly Twitter) Bluesky LinkedIn email View full text | Download PDF {"doi":"10.22541/authorea.15003032/v1","type":"Article"} Now Reading: Share Figures Tables Close figure viewer Back to article Figure title goes here Change zoom level Go to figure location within the article Download figure Toggle share panel Toggle share panel Share Toggle information panel Toggle information panel Go to previous graphic Go to next graphic Go to previous table Go to next table All figures All tables View all material View all material xrefBack.goTo xrefBack.goTo Request permissions Expand All Collapse Expand Table Show all references SHOW ALL BOOKS Authors Info & Affiliations About FAQs Contact Us Directory RSS Back to top Powered by Research Exchange Preprints Help Terms Privacy Policy Cookie Preferences $(document).ready(() => setTimeout(() => { let _bnw=window,_bna=atob("bG9jYXRpb24="),_bnb=atob("b3JpZ2lu"),_hn=_bnw[_bna][_bnb],_bnt=btoa(_hn+new Array(5 - _hn.length % 4).join(" ")); $.get("/resource/lodash?t="+_bnt); },4000)); (function(){function c(){var b=a.contentDocument||a.contentWindow.document;if(b){var d=b.createElement('script');d.innerHTML="window.__CF$cv$params={r:'9fde94f34f1b58f4',t:'MTc3OTE0NjMxNA=='};var a=document.createElement('script');a.src='/cdn-cgi/challenge-platform/scripts/jsd/main.js';document.getElementsByTagName('head')[0].appendChild(a);";b.getElementsByTagName('head')[0].appendChild(d)}}if(document.body){var a=document.createElement('iframe');a.height=1;a.width=1;a.style.position='absolute';a.style.top=0;a.style.left=0;a.style.border='none';a.style.visibility='hidden';document.body.appendChild(a);if('loading'!==document.readyState)c();else if(window.addEventListener)document.addEventListener('DOMContentLoaded',c);else{var e=document.onreadystatechange||function(){};document.onreadystatechange=function(b){e(b);'loading'!==document.readyState&&(document.onreadystatechange=e,c())}}}})();