Seagrass deterrence to mesograzer herbivory: evidence from mesocosm experiments and feeding preference trials

Steele, LaTina; Valentine, John F.

doi:10.3354/meps11127

Cited by 25 publications

(12 citation statements)

References 53 publications

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“…While we hypothesized that changes in choice patterns and feeding rates were the result of C:N ratios, it is also possible that an undocumented and unquantified covarying variable influenced this trend. For example, C:N may be correlated with phenolics or other chemical defenses that would alter feeding patterns [68]. Moreover, we know little about the levels of ecological significance in these ratios and a better understanding of food web dynamics may be attained by determining variability in C:N ratios and the ensuing food web consequences.…”

Section: Discussionmentioning

confidence: 99%

Herbivory of oil-exposed submerged aquatic vegetation Ruppia maritima

Martin

Swenson

2018

PLoS ONE

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Oil spills, such as the Deepwater Horizon spill in the Gulf of Mexico, have the potential to dramatically alter coastal food webs through a variety of mechanisms. While oil can have direct impacts on primary producers through toxicity and shading, it is also possible that more subtle, indirect changes to the interactions among organisms could alter energy flow through the ecosystem. Here, we present the results of a series of manipulative experiments to determine the impacts of oil exposure on herbivory of Ruppia maritima, one of the most common species of submerged vegetation found in the region impacted by the 2010 Deepwater Horizon oil spill. In previous experiments, R. maritima was grown in a range of manipulated sediment oil concentrations. Using plant tissue from this experiment, we analyzed the effects of oil on plant chemical composition and found that plant carbon:nitrogen ratio (C:N) was reduced by as much as 21% in plants exposed to higher concentrations of oil. Given that nitrogen plays a key role in herbivore preference patterns, we performed herbivory assays and found oil-contaminated plants were preferred by herbivores in choice trials, although subsequent no-choice experiments indicated herbivores consumed less oil-contaminated tissue. We hypothesize the reason for this is that more tissue of higher C:N content is needed to meet similar metabolic demands while avoiding the potentially negative impacts of feeding on contaminated tissues. These results indicate that substantial food web alterations may occur via enhanced consumption of oil-exposed plants and provides vital information necessary to assess the large-scale impact of oil on submerged macrophytes.

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Section: Discussionmentioning

confidence: 99%

Herbivory of oil-exposed submerged aquatic vegetation Ruppia maritima

Martin

Swenson

2018

PLoS ONE

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“…Similarly, grazer-damage has been reported to induce a different plant response than physical damage alone [ 33 , 34 , 35 ]. Despite these indications, in a recent study, Steele and Valentine [ 36 ] found no induced change in the palatability of two tropical seagrass species to the isopod Paracerceis caudata after a 15-day induction experiment. Therefore, in order to understand the general significance of inducible defences in seagrasses we first need to provide a solid assessment of whether mesograzers are able to induce defences that deter consumption and how this may vary among different seagrass and mesograzer species.…”

Section: Introductionmentioning

confidence: 98%

Specificity in Mesograzer-Induced Defences in Seagrasses

Martínez-Crego¹,

Arteaga²,

Ueber

et al. 2015

PLoS ONE

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Grazing-induced plant defences that reduce palatability to herbivores are widespread in terrestrial plants and seaweeds, but they have not yet been reported in seagrasses. We investigated the ability of two seagrass species to induce defences in response to direct grazing by three associated mesograzers. Specifically, we conducted feeding-assayed induction experiments to examine how mesograzer-specific grazing impact affects seagrass induction of defences within the context of the optimal defence theory. We found that the amphipod Gammarus insensibilis and the isopod Idotea chelipes exerted a low-intensity grazing on older blades of the seagrass Cymodocea nodosa, which reflects a weak grazing impact that may explain the lack of inducible defences. The isopod Synischia hectica exerted the strongest grazing impact on C. nodosa via high-intensity feeding on young blades with a higher fitness value. This isopod grazing induced defences in C. nodosa as indicated by a consistently lower consumption of blades previously grazed for 5, 12 and 16 days. The lower consumption was maintained when offered tissues with no plant structure (agar-reconstituted food), but showing a reduced size of the previous grazing effect. This indicates that structural traits act in combination with chemical traits to reduce seagrass palatability to the isopod. Increase in total phenolics but not in C:N ratio and total nitrogen of grazed C. nodosa suggests chemical defences rather than a modified nutritional quality as primarily induced chemical traits. We detected no induction of defences in Zostera noltei, which showed the ability to replace moderate losses of young biomass to mesograzers via compensatory growth. Our study provides the first experimental evidence of induction of defences against meso-herbivory that reduce further consumption in seagrasses. It also emphasizes the relevance of grazer identity in determining the level of grazing impact triggering resistance and compensatory responses of different seagrass species.

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“…Seagrasses exposed to herbivory may decline or die-off, exhibit tolerance through compensatory or super-compensatory growth, or display resistance by altering their physiology or chemistry through methods such as nutrient or carbohydrate re-routing or by producing secondary metabolites (Cebrian et al 1998, Ricklefs and Miller 1999, Vergés et al 2008, Burnell et al 2013a, Steele and Valentine 2015. The tolerance of primary producers to different kinds of herbivory differs by species-though it can also be induced in response to herbivory (e.g., Burnell et al 2013a, Sanmarti et al 2014-and this differential tolerance can have implications for seagrass community composition.…”

Section: The Role Of Seagrass In Mediating the Strength Of Top-down Pmentioning

confidence: 99%

“…Similarly, in Watamu National Marine Park, Kenya, feeding preferences of the teleost herbivore Calotomus carolinus are inversely correlated to the carbon fiber content of primary producer species (Mariani and Alcoverro 1999, Table 1). The relationship between nutrient ratios, plant defenses, and herbivore feeding preference is further obscured by the fact that plant characteristics can fluctuate across space, time, species, and individual (e.g., Fourqurean et al 2005, Hays 2005, Tomas et al 2011, Steele and Valentine 2015. This complicates drawing patterns because multiple chemical variables can change concurrently, making attribution of herbivory to a single compound or group of compounds difficult.…”

Section: The Role Of Seagrass In Mediating the Strength Of Top-down Pmentioning

confidence: 99%

“…Finally, different herbivores place varying levels of importance on each of these seagrass qualities (Prado and Heck 2011) meaning that understanding herbivore feeding preference requires not only comprehensive knowledge of seagrass chemical properties, but also insight into which of those properties local herbivores consider most. Despite the complex relationship between chemical properties and herbivory, investigations into a generalizable pattern are important as these chemical properties can significantly influence herbivory rates (e.g., Steele and Valentine 2015).…”

Section: The Role Of Seagrass In Mediating the Strength Of Top-down Pmentioning

confidence: 99%

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Effects of Catastrophic Seagrass Loss and Predation Risk on the Ecological Structure and Resilience of a Model Seagrass Ecosystem

Nowicki¹

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It takes a village to write a dissertation, and I have many people to thank. First thanks go to my graduate committee, mentioned above, for their patience and constant guidance throughout the PhD process. Most importantly, thanks to Mike Heithaus, whose guidance, encouragement, baseline sampling, and dislike of waffle words allowed me to grow from a timid postgraduate into a fledgling scientist. I am still awed by your productivity and constant good humor, and thanks to you I have adopted a can-do attitude in my research and my professional life. Thank you for everything. As for the lab, thanks in particular to Jordy Thomson for showing me the ropes of Shark Bay, including how to run a boat, break a boat, fix a boat, and call for assistance when you can't fix a boatremember, every crisis is an opportunity. Also thanks for introducing me to Barret's Privateers, cleanskins, and most importantly, Spongebob. Kirk Gastrich deserves many thanks for his constant guidance and advice on all things Shark Bay, for tireless efforts to get the work done, good conversations at the captain's table, and for having an empty bag of chips when we needed it most. Derek Burkholder was also instrumental in helping complete this dissertation, particularly in the care and troubleshooting of our research fleet, of which he is the ultimate authority. I am also in his debt for the gargantuan baseline dataset which only a person of his resolve could build and which made chapter III possible. Thanks to Cindy Bessey (and Brett) for rescuing us from the middle of the outback, acting as a sounding board for ideas, and being the boots on the ground when I was 13,000 miles away. Thanks also to Phil, Adam, Jeremy, Diana, Beth, Camila, Jimmy, and the rest of the Heithaus lab, who made contributions great and small to my development as a grad student and scientist. vii My work in Shark Bay was made possible by the tireless efforts of an army of volunteers, specifically Robin Sarabia,

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Seagrass deterrence to mesograzer herbivory: evidence from mesocosm experiments and feeding preference trials

Abstract: Running head: Effects of mesograzer feeding on seagrass phenolics This is a pre-print version of the manuscript. It is not the final copy-edited version, but all figures are identical to those in the final, published article.

Cited by 25 publications

References 53 publications

Herbivory of oil-exposed submerged aquatic vegetation Ruppia maritima

Herbivory of oil-exposed submerged aquatic vegetation Ruppia maritima

Specificity in Mesograzer-Induced Defences in Seagrasses

Effects of Catastrophic Seagrass Loss and Predation Risk on the Ecological Structure and Resilience of a Model Seagrass Ecosystem

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