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Burnett NP, Gaylord B. Flow, form, and force: methods and frameworks for field studies of macroalgal biomechanics. JOURNAL OF EXPERIMENTAL BOTANY 2022; 73:1122-1138. [PMID: 34791153 DOI: 10.1093/jxb/erab498] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2021] [Accepted: 11/10/2021] [Indexed: 06/13/2023]
Abstract
Macroalgae are ecologically important organisms that often inhabit locations with physically challenging water motion. The biomechanical traits that permit their survival in these conditions have been of interest to biologists and engineers alike, but logistical and technical challenges of conducting investigations in macroalgal habitats have often prevented optimal study of these traits. Here, we review field methods for quantifying three major components of macroalgal biomechanics in moving water: fluid flow, macroalgal form, and hydrodynamic force. The implementation of some methodologies is limited due to the current state and accessibility of technology, but many of these limitations can be remedied by custom-built devices, borrowing techniques from other systems, or shifting lab-based approaches to the field. We also describe several frameworks for integrating flow, form, and force data that can facilitate comparisons of macroalgal biomechanics in field settings with predictions from theory and lab-based experiments, or comparisons between flow conditions, habitats, and species. These methods and frameworks, when used on scales that are relevant to the examined processes, can reveal mechanistic information about the functional traits that permit macroalgae to withstand physically challenging water motion in their habitats, using the actual fluid flows, macroalgal forms, and physical forces that occur in nature.
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Affiliation(s)
- Nicholas P Burnett
- Department of Neurobiology, Physiology, and Behavior, University of California - Davis, Davis, CA, USA
| | - Brian Gaylord
- Bodega Marine Laboratory, University of California - Davis, CA, USA
- Department of Evolution and Ecology, University of California - Davis, Davis, CA, USA
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2
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Millar R, Houghton JDR, Kregting L. The stress and strain of life - how differences in the mechanical properties and cellular composition enable the kelp Laminaria digitata to thrive in different hydrodynamic environments. MARINE ENVIRONMENTAL RESEARCH 2021; 169:105330. [PMID: 33940312 DOI: 10.1016/j.marenvres.2021.105330] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Revised: 03/20/2021] [Accepted: 04/04/2021] [Indexed: 06/12/2023]
Abstract
Sessile organisms such as macroalgae located in the intertidal and shallow subtidal zones are subject to a hydrodynamically diverse environment, controlling the variation of intraspecific morphology and distribution. Kelp forests experience both waves and/or currents, yet, how kelp blade material mechanically differs between these various hydrodynamic environments and what drives the variation in strength and extensibility are not fully understood. Here, the mechanical properties, cellular composition and blade tissue thickness of the meristematic region and distal tips of the kelp Laminaria digitata blades were quantified and compared between seasons and among three hydrodynamic environments: wave dominated, current dominated and a benign hydrodynamic environment. Kelps associated with energetic environments, generally tended to be stronger yet more extensible than those growing in the benign hydrodynamic environment. Higher extensibility was located at the meristematic region whereas tissue was stronger in the distal tip of the blade. Linking both cellular composition and mechanical properties, results suggest enhancement of medulla cells in the meristematic region increases extensibility, potentially protecting the thallus during increased storm activity while growing in a wave/current exposed habitat. Investment in cortex cells towards the tip of the blade suggests an increase in strength of the region, which is susceptible to breakage. However, the lack of variation in the proportion of medulla and cortex cellular layers between distinct hydrodynamic environments revealed that the potential overall strategy for avoiding breakage in energetic hydrodynamic environments is that of investing energy into the increased thickness of blade tissue.
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Affiliation(s)
- Rachel Millar
- School of Natural and Built Environment, Queen's University Belfast, Stranmillis Road, Belfast BT9 5AG, Northern Ireland, UK; Queen's University Marine Laboratory, Queen's University Belfast, 12-13 the Strand, Portaferry, BT22 1PF, UK.
| | - Jonathan D R Houghton
- School of Biological Sciences, Queen's University Belfast, 19 Chlorine Gardens, Belfast, BT9 5DL, UK
| | - Louise Kregting
- School of Natural and Built Environment, Queen's University Belfast, Stranmillis Road, Belfast BT9 5AG, Northern Ireland, UK; Queen's University Marine Laboratory, Queen's University Belfast, 12-13 the Strand, Portaferry, BT22 1PF, UK
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3
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Liversage K, Kotta J, Kuprijanov I, Rätsep M, Nõomaa K. A trophic cascade facilitates native habitat providers within assemblages of multiple invasive marine species. Ecosphere 2021. [DOI: 10.1002/ecs2.3621] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Affiliation(s)
- K. Liversage
- Estonian Marine Institute University of Tartu Mäealuse 14 Tallinn12618Estonia
| | - J. Kotta
- Estonian Marine Institute University of Tartu Mäealuse 14 Tallinn12618Estonia
| | - I. Kuprijanov
- Department of Marine Systems Tallinn University of Technology Akadeemia tee 15a Tallinn12618Estonia
| | - M. Rätsep
- Estonian Marine Institute University of Tartu Mäealuse 14 Tallinn12618Estonia
| | - K. Nõomaa
- Estonian Marine Institute University of Tartu Mäealuse 14 Tallinn12618Estonia
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4
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Fulton-Bennett HK. Sublethal biomass loss in Egregia menziesii (Phaeophyceae) reveals diffuse meristem tissue. JOURNAL OF PHYCOLOGY 2021; 57:1084-1088. [PMID: 33624309 DOI: 10.1111/jpy.13152] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Accepted: 02/04/2021] [Indexed: 06/12/2023]
Abstract
Sublethal biomass loss has been found to have a variety of effects on marine macroalgae, from decreasing reproductive output to increasing individual survival and frond density. The ability of an individual to recover and persist through herbivore and wave damage is facilitated by the location of several meristematic growth regions throughout an individual. In kelps (Order Laminariales), meristems are found basally at the holdfast, at the base of each blade, and/or apically on each frond. In the intertidal kelp Egregia menziesii, fronds are thought to have an intercalary meristem at a transition zone between the main frond's midrib and a small terminal lamina. This study examined the effect of removing the terminal blade and transition zone on the elongation of the frond and found no significant difference in growth, contrary to expectations. Elongation occurred in the 30 cm of midrib at the apical end of fronds and was not isolated at the base of the terminal lamina as was previously thought. These results indicate the presence of a diffuse meristematic growth region that has not been reported in other kelps and may be an advantage for this intertidal species.
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Kobluk HM, Gladstone K, Reid M, Brown K, Krumhansl KA, Salomon AK. Indigenous knowledge of key ecological processes confers resilience to a small‐scale kelp fishery. PEOPLE AND NATURE 2021. [DOI: 10.1002/pan3.10211] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Affiliation(s)
- Hannah M. Kobluk
- School of Resource and Environmental Management Simon Fraser University Burnaby BC Canada
| | | | - Mike Reid
- Heiltsuk Nation Bella Bella BC Canada
- Heiltsuk Integrated Resource Management Department Bella Bella BC Canada
| | - Kelly Brown
- Heiltsuk Nation Bella Bella BC Canada
- Heiltsuk Integrated Resource Management Department Bella Bella BC Canada
| | - Kira A. Krumhansl
- Fisheries and Oceans Canada Bedford Institute of Oceanography Dartmouth Nova Scotia Canada
| | - Anne K. Salomon
- School of Resource and Environmental Management Simon Fraser University Burnaby BC Canada
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6
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Burnett NP, Koehl MAR. Age affects the strain-rate dependence of mechanical properties of kelp tissues. AMERICAN JOURNAL OF BOTANY 2021; 108:769-776. [PMID: 33993474 DOI: 10.1002/ajb2.1662] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/06/2020] [Accepted: 01/07/2021] [Indexed: 06/12/2023]
Abstract
PREMISE The resistance of macroalgae to hydrodynamic forces imposed by ambient water motion depends in part on the mechanical properties of their tissues. In wave-swept habitats, tissues are stretched (strained) at different rates as hydrodynamic forces change. Previous studies of mechanical properties of macroalgal tissues have used either a single strain rate or a small range of strain rates. Therefore, our knowledge of the mechanical properties of macroalgae is limited to a narrow fraction of the strain rates that can occur in nature. In addition, although mechanical properties of macroalgal tissues change with age, the effect of age on the strain-rate dependence of their mechanical behavior has not been documented. METHODS Using the kelp Egregia menziesii, we measured how high strain rate (simulating wave impingement) and low strain rate (simulating wave surge) affected mechanical properties of frond tissues of various ages. RESULTS Stiffness of tissues of all ages increased with strain rate, whereas extensibility was unaffected. Strength and toughness increased with strain rate for young tissue but were unaffected by strain rate for old tissue. CONCLUSIONS Young tissue is weaker than old tissue and, therefore, the most susceptible to breakage from hydrodynamic forces. The increased strength of young tissue at high strain rates can help the frond resist breaking when pulled rapidly during wave impingement, when hydrodynamic forces are largest. Because breakage of young tissue can remove a frond's meristem and negatively impact the survival of the whole kelp, strain-rate dependence of the young tissue's strength can enhance kelp's survival.
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Affiliation(s)
- Nicholas P Burnett
- Department of Integrative Biology, University of California, Berkeley, CA, 94720, USA
| | - M A R Koehl
- Department of Integrative Biology, University of California, Berkeley, CA, 94720, USA
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Demes KW, Starko S, Harley CDG. Multiple stressors drive convergent evolution of performance properties in marine macrophytes. THE NEW PHYTOLOGIST 2021; 229:2311-2323. [PMID: 33037641 DOI: 10.1111/nph.16994] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2020] [Accepted: 10/02/2020] [Indexed: 06/11/2023]
Abstract
Extreme environments have driven the evolution of some of the most inspiring adaptations in nature. In the intertidal zone of wave-swept shores, organisms face physical forces comparable to hurricanes and must further endure thermal and desiccation stress during low tides, compromising their physiological and biomechanical performance. We examine how these multiple stressors have influenced the evolution of tissue properties during desiccation using eight phylogenetically independent pairs of intertidal and subtidal macrophytes. Intertidal species generally lost water more slowly than their subtidal counterparts, presumably as an adaption to regular emersion. Under partial desiccation, breaking force, strength, and extensibility of intertidal species generally exceeded those of subtidal species, although important differences existed among phylogenetic pairs. This was often true even when subtidal relatives resisted greater forces or were more extensible under full hydration. The interacting effects of mechanical forces and desiccation during low tide are likely a major selective agent in determining macrophyte performance and fitness. Overall, we found that lineages that have independently evolved to occupy the wave-swept intertidal have converged on performance metrics that are likely to be adaptive to the interacting stressors associated with their extreme niches.
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Affiliation(s)
- Kyle W Demes
- Department of Institutional Strategic Awards, Simon Fraser University, Burnaby, BC, V5A 1S6, Canada
- Department of Zoology, The University of British Columbia, Vancouver, BC, V6T 1Z4, Canada
| | - Samuel Starko
- Department of Biology, The University of British Columbia, Vancouver, BC, V6T 1Z4, Canada
- Department of Biology, University of Victoria, Victoria, BC, V8W 2Y2, Canada
| | - Christopher D G Harley
- Department of Zoology, The University of British Columbia, Vancouver, BC, V6T 1Z4, Canada
- Institute for the Oceans and Fisheries, The University of British Columbia, Vancouver, BC, V6T 1Z4, Canada
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Coleman LJM, Martone PT. Morphological plasticity in the kelp Nereocystis luetkeana (Phaeophyceae) is sensitive to the magnitude, direction, and location of mechanical loading. JOURNAL OF PHYCOLOGY 2020; 56:1414-1427. [PMID: 32602559 DOI: 10.1111/jpy.13043] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Accepted: 05/27/2020] [Indexed: 06/11/2023]
Abstract
Nereocystis luetkeana is a canopy-forming kelp that exhibits morphological plasticity across hydrodynamic gradients, producing broad, undulate blades in slow flow and narrow, flattened blades in fast flow, enabling thalli to reduce drag while optimizing photosynthesis. While the functional significance of this phenomenon has been well studied, the developmental and physiological mechanisms that facilitate the plasticity remain poorly understood. In this study, we conducted three experiments to characterize how the (1) magnitude, (2) direction, and (3) location of plasticity-inducing mechanical stimuli affect the morphology of Nereocystis blades. We found that applying a gradient of tensile force caused blades to grow progressively longer, narrower, less ruffled, and heavier in a linear fashion, suggesting that Nereocystis is equally well adapted for all conditions within its hydrodynamic niche. We also found that applying tension transversely across blades caused the growth response to rotate 90°, indicating that there is no substantial separation between the sites of stimulus perception and response and suggesting that a long-distance signaling mechanism, such as a hormone, is unlikely to mediate this phenomenon. Meristoderm cells showed morphological changes that paralleled those of their respective blades in this experiment, implying that tissue-level morphology is influenced by cell growth. Finally, we found that plasticity was only induced when tension was applied directly to the growing tissue, reinforcing that long-distance signaling is probably not involved and possibly indicating that the mechanism on display generally requires an intercalary meristem to facilitate mechanoperception.
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Affiliation(s)
- Liam J M Coleman
- Department of Botany & Biodiversity Research Centre, University of British Columbia, 6270 University Blvd, Vancouver, British Columbia, V6T 1Z4, Canada
| | - Patrick T Martone
- Department of Botany & Biodiversity Research Centre, University of British Columbia, 6270 University Blvd, Vancouver, British Columbia, V6T 1Z4, Canada
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9
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Starko S, Demes KW, Neufeld CJ, Martone PT. Convergent evolution of niche structure in Northeast Pacific kelp forests. Funct Ecol 2020. [DOI: 10.1111/1365-2435.13621] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Affiliation(s)
- Samuel Starko
- Department of Botany & Biodiversity Research Centre University of British Columbia Vancouver BC Canada
- Department of Biology University of Victoria Victoria BC Canada
- Bamfield Marine Sciences Centre Bamfield BC Canada
| | - Kyle W. Demes
- Institutional Strategic Awards Simon Fraser University Burnaby BC Canada
| | | | - Patrick T. Martone
- Department of Botany & Biodiversity Research Centre University of British Columbia Vancouver BC Canada
- Bamfield Marine Sciences Centre Bamfield BC Canada
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10
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Demes KW, Pruitt JN. Individuality in seaweeds and why we need to care. JOURNAL OF PHYCOLOGY 2019; 55:247-256. [PMID: 30802959 DOI: 10.1111/jpy.12845] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2018] [Accepted: 02/18/2019] [Indexed: 06/09/2023]
Abstract
Documenting the causes and consequences of intraspecific variation forms the foundation of much of evolutionary ecology. In this Perspectives piece, we review the importance of individual variation in ecology and evolution, argue that contemporary phycology often overlooks this foundational biological unit, and highlight how this lack of attention has potentially constrained our understanding of seaweeds. We then provide some suggestions of promising but underrepresented approaches, for instance: conducting more studies and analyses at the level of the individual; designing studies to evaluate heritability and genetic regulation of traits; and measuring associations between individual variation in functional traits and ecological outcomes. We close by highlighting areas of phycological research (e.g., population biology, ecology, aquaculture, climate change management) that could benefit immediately from including a focus on individual variation. Algae, for their part, provide us with a powerful and diverse set of ecological and evolutionary traits to explore these topics. There is much to be discovered.
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Affiliation(s)
- Kyle W Demes
- Department of Institutional Strategic Awards, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia, Canada, V5A 1S6
- Department of Zoology, The University of British Columbia, 2329 West Mall, Vancouver, British Columbia, Canada, V6T 1Z4
| | - Jonathan N Pruitt
- Department of Psychology, Neurobiology and Behaviour, McMaster University, Hamilton, Ontario, Canada, L8S 4K1
- Marine Science Institute, University of California Santa Barbara, Santa Barbara, California, 93117, USA
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11
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Burnett NP, Koehl MAR. Mechanical properties of the wave-swept kelp Egregia menziesii change with season, growth rate and herbivore wounds. J Exp Biol 2019; 222:jeb190595. [PMID: 30679240 DOI: 10.1242/jeb.190595] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2018] [Accepted: 01/17/2019] [Indexed: 11/20/2022]
Abstract
The resistance of macroalgae to damage by hydrodynamic forces depends on the mechanical properties of their tissues. Although factors such as water-flow environment, algal growth rate and damage by herbivores have been shown to influence various material properties of macroalgal tissues, the interplay of these factors as they change seasonally and affect algal mechanical performance has not been worked out. We used the perennial kelp Egregia menziesii to study how the material properties of the rachis supporting a frond changed seasonally over a 2 year period, and how those changes correlated with seasonal patterns of the environment, growth rate and herbivore load. Rachis tissue became stiffer, stronger and less extensible with age (distance from the meristem). Thus, slowly growing rachises were stiffer, stronger and tougher than rapidly growing ones. Growth rates were highest in spring and summer when upwelling and long periods of daylight occurred. Therefore, rachis tissue was most resistant to damage in the winter, when waves were large as a result of seasonal storms. Herbivory was greatest during summer, when rachis growth rates were high. Unlike other macroalgae, E. menziesii did not respond to herbivore damage by increasing rachis tissue strength, but rather by growing in width so that the cross-sectional area of the wounded rachis was increased. The relative timing of environmental factors that affect growth rates (e.g. upwelling supply of nutrients, daylight duration) and of those that can damage macroalgae (e.g. winter storms, summer herbivore outbreaks) can influence the material properties and thus the mechanical performance of macroalgae.
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Affiliation(s)
- Nicholas P Burnett
- Department of Integrative Biology, University of California, Berkeley, CA 94720, USA
- Department of Neurobiology, Physiology, and Behavior, University of California, Davis, CA 95616, USA
| | - M A R Koehl
- Department of Integrative Biology, University of California, Berkeley, CA 94720, USA
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12
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Lees LE, Krueger-Hadfield SA, Clark AJ, Duermit EA, Sotka EE, Murren CJ. Nonnative Gracilaria vermiculophylla tetrasporophytes are more difficult to debranch and are less nutritious than gametophytes. JOURNAL OF PHYCOLOGY 2018; 54:471-482. [PMID: 29676788 DOI: 10.1111/jpy.12746] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2017] [Accepted: 03/22/2018] [Indexed: 06/08/2023]
Abstract
Theory predicts that the maintenance of haplodiplontic life cycles requires ecological differences between the haploid gametophytes and diploid sporophytes, yet evidence of such differences remain scarce. The haplodiplontic red seaweed Gracilaria vermiculophylla has invaded the temperate estuaries of the Northern Hemisphere, where it commonly modifies detrital and trophic pathways. In native populations, abundant hard substratum enables spore settlement, and gametophyte:tetrasporophyte ratios are ~40:60. In contrast, many non-native populations persist in soft-sediment habitats without abundant hard substratum, and can be 90%-100% tetrasporophytic. To test for ecologically relevant phenotypic differences, we measured thallus morphology, protein content, organic content, "debranching resistance" (i.e., tensile force required to remove a branch from its main axis node), and material properties between male gametophytes, female gametophytes, and tetrasporophytes from a single, nonnative site in Charleston Harbor, South Carolina, USA in 2015 and 2016. Thallus length and surface area to volume ratio differed between years, but were not significantly different between ploidies. Tetrasporophytes had lower protein content than gametophytes, suggesting the latter may be more attractive to consumers. More force was required to pull a branch from the main axis of tetrasporophytes relative to gametophytes. A difference in debranching resistance may help to maintain tetrasporophyte thallus durability relative to gametophytes, providing a potential advantage in free-floating populations. These data may shed light on the invasion ecology of an important ecosystem engineer, and may advance our understanding of life cycle evolution and the maintenance of life cycle diversity.
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Affiliation(s)
- Lauren E Lees
- Grice Marine Laboratory, College of Charleston, 205 Fort Johnson Rd, Charleston, South Carolina, 29414, USA
- Department of Biology, College of Charleston, 66 George Street, Charleston, South Carolina, 29424, USA
| | - Stacy A Krueger-Hadfield
- Grice Marine Laboratory, College of Charleston, 205 Fort Johnson Rd, Charleston, South Carolina, 29414, USA
- Department of Biology, College of Charleston, 66 George Street, Charleston, South Carolina, 29424, USA
- Department of Biology, University of Alabama at Birmingham, Birmingham, Alabama, 35924, USA
| | - Andrew J Clark
- Department of Biology, College of Charleston, 66 George Street, Charleston, South Carolina, 29424, USA
| | - Elizabeth A Duermit
- Grice Marine Laboratory, College of Charleston, 205 Fort Johnson Rd, Charleston, South Carolina, 29414, USA
- Department of Biology, College of Charleston, 66 George Street, Charleston, South Carolina, 29424, USA
| | - Erik E Sotka
- Grice Marine Laboratory, College of Charleston, 205 Fort Johnson Rd, Charleston, South Carolina, 29414, USA
- Department of Biology, College of Charleston, 66 George Street, Charleston, South Carolina, 29424, USA
| | - Courtney J Murren
- Department of Biology, College of Charleston, 66 George Street, Charleston, South Carolina, 29424, USA
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Starko S, Martone PT. Evidence of an evolutionary-developmental trade-off between drag avoidance and tolerance strategies in wave-swept intertidal kelps (Laminariales, Phaeophyceae). JOURNAL OF PHYCOLOGY 2016; 52:54-63. [PMID: 26987088 DOI: 10.1111/jpy.12368] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Accepted: 10/13/2015] [Indexed: 06/05/2023]
Abstract
Kelps are a clade of morphologically diverse, ecologically important habitat-forming species. Many kelps live in wave-swept environments and are exposed to chronic flow-induced stress. In order to grow and survive in these harsh environments, kelps can streamline (reducing drag coefficient) to avoid drag or to increase attachment and breakage force to tolerate it. We aimed to quantify the drag tolerance and streamlining strategies of kelps from wave-swept intertidal habitats. We measured drag coefficient and tenacity of populations from eight kelp species over a wide range of sizes to determine whether kelps avoid dislodgement by reducing drag coefficient or by increasing tenacity as they grow, and whether these traits are traded off. We employed phylogenetic comparative methods to rule out potentially confounding effects of species' relatedness. There was a significant negative relationship between drag avoidance and tolerance strategies, even after incorporating phylogeny. Kelps that were more tenacious were less able to reduce drag, resulting in a continuum from "tolerators" to "streamliners," with some species demonstrating intermediate, mixed strategies. Drag and tenacity were correlated with geometric properties (i.e., second moment of area) of the stipe in large kelps. Results presented in this study suggest that kelps are either strong or streamlined, but not both. This continuum is consistent with avoidance and tolerance trade-offs that have been documented in many different biological systems and may have widespread implications for the evolution of large macroalgae, perhaps driving morphological diversity within this group.
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Affiliation(s)
- Samuel Starko
- Department of Botany and Beaty Biodiversity Research Centre, University of British Columbia, Vancouver, British Columbia, Canada, V6T1Z4
- Bamfield Marine Sciences Centre, 100 Pachena Road, Bamfield, British Columbia, Canada
| | - Patrick T Martone
- Department of Botany and Beaty Biodiversity Research Centre, University of British Columbia, Vancouver, British Columbia, Canada, V6T1Z4
- Bamfield Marine Sciences Centre, 100 Pachena Road, Bamfield, British Columbia, Canada
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14
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Krumhansl KA, Demes KW, Carrington E, Harley CDG. Divergent growth strategies between red algae and kelps influence biomechanical properties. AMERICAN JOURNAL OF BOTANY 2015; 102:1938-44. [PMID: 26546127 DOI: 10.3732/ajb.1500289] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/19/2015] [Accepted: 10/01/2015] [Indexed: 06/05/2023]
Abstract
PREMISE OF THE STUDY Morphology and material properties are the main components of the mechanical design of organisms, with species groups developing different optimization strategies in the context of their physical environment. For intertidal and subtidal seaweeds, possessing highly flexible and extensible tissues allows individuals to bend and reconfigure in flow, thereby reducing drag. Previous research has shown that aging may compromise these qualities. Tissue age increases with distance from the blade's meristem, which differs in its position on kelps and red algae. Here, we assess whether longitudinal patterns of blade material properties differ between these two algal groups according to tissue age. METHODS We performed tensile tests on tissues samples excised from various positions along the extent of blades in nine kelp species (basal growth) and 15 species of red algae (apical growth). KEY RESULTS We found that older tissues were less flexible and extensible than younger tissues in all species tested. As predicted, tissue near the basal meristem in kelp was more flexible and extensible than older tissue at the blade's distal end. The opposite pattern was observed for red algae, with the most flexible and extensible tissues found near the apical meristem at the distal ends of blades. CONCLUSIONS We propose that divergent patterns in the distribution of material properties along blades may have different consequences for the performance of kelps and red algae. The positioning of younger tissues at the blade base for kelps may enable these species to attain larger body sizes in wave-swept habitats.
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Affiliation(s)
- Kira A Krumhansl
- Department of Resource and Environmental Management, Simon Fraser University, 622 Strand Hall Annex 8888 University Dr. Burnaby, B.C. Canada V5A 1S6 Hakai Institute, PO Box 309, Heriot Bay, B.C. Canada V0P 1H0
| | - Kyle W Demes
- Hakai Institute, PO Box 309, Heriot Bay, B.C. Canada V0P 1H0 Department of Zoology, University of British Columbia, 6270 University Blvd. Vancouver, B.C. Canada V6T 1Z4
| | - Emily Carrington
- Department of Biology and Friday Harbor Laboratories, University of Washington, 620 University Road. Friday Harbor, WA USA 98250
| | - Christopher D G Harley
- Department of Zoology, University of British Columbia, 6270 University Blvd. Vancouver, B.C. Canada V6T 1Z4
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15
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De Bettignies T, Wernberg T, Lavery PS, Vanderklift MA, Gunson JR, Symonds G, Collier N. Phenological decoupling of mortality from wave forcing in kelp beds. Ecology 2015; 96:850-61. [PMID: 26236880 DOI: 10.1890/13-2365.1] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Kelps often live in a harsh hydrodynamic environment where wave-driven dislodgement of individuals can alter the biodiversity and functioning of reef systems, and increase production in coastal ecosystems adjacent to reefs. The current paradigm is that winter storms tear kelps from reefs once hydrodynamic forces exceed attachment or tissue strength--a threshold response that implies a pulsed relationship between wave forces and dislodgement. Here, we challenge this understanding by showing how kelp phenology can decouple susceptibility to dislodgement from seasonal patterns in wave forces. We measured kelp dislodgement rates and hydrodynamic forces at nine subtidal reefs over two years (n = 4320 kelps tagged and monitored). Contrary to expectation, we found relatively low and constant dislodgement rates for all reefs (13% +/- 6% [mean per season +/- SD]) in spite of a strong temporal pattern in wave action and extreme water velocities (winter peaks up to 3-4 m/s). A biomechanical model, based on the balance between kelp attachment strength and hydrodynamic drag, demonstrated that severe reduction in individual kelp size toward winter (>50% decrease in biomass for all sites) minimized drag and made the kelps less susceptible to high water velocities, allowing individuals to survive storm velocities over 3-4 m/s. We conclude that the timing of reduced susceptibility to disturbance, through the seasonal reduction of individual kelp biomass that coincides with times of highest water velocities is critical to the dynamics of kelp dislodgement and survival. We propose that phenological processes maintain many kelp beds in a higher degree of population stability and equilibrium with hydrodynamic forces than previously believed.
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Abstract
Epiphytic algae grow on other algae rather than hard substrata, perhaps circumventing competition for space in marine ecosystems. Aquatic epiphytes are widely thought to negatively affect host fitness; it is also possible that epiphytes benefit from associating with hosts. This study explored the biomechanical costs and benefits of the epiphytic association between the intertidal brown algal epiphyte Soranthera ulvoidea and its red algal host Odonthalia floccosa. Drag on epiphytized and unepiphytized hosts was measured in a recirculating water flume. A typical epiphyte load increased drag on hosts by ~50%, increasing dislodgment risk of epiphytized hosts compared with hosts that did not have epiphytes. However, epiphytes were more likely to dislodge from hosts than hosts were to dislodge from the substratum, suggesting that drag added by epiphytes may not be mechanically harmful to hosts if epiphytes break first. Concomitantly, epiphytes experienced reduced flow when attached to hosts, perhaps allowing them to grow larger or live in more wave-exposed areas. Biomechanical interactions between algal epiphytes and hosts are complex and not necessarily negative, which may partially explain the evolution and persistence of epiphytic relationships.
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Affiliation(s)
- Laura M Anderson
- Department of Botany and Biodiversity Research Centre, University of British Columbia, 6270 University Boulevard, Vancouver, BC V6T 1Z4, Canada
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