Degradation state of algal diets affects fatty acid composition but not size of red urchin gonads

Raymond, Wendel W.; Lowe, Alexander T.; Galloway, Aaron W. E.

doi:10.3354/meps10888

Cited by 10 publications

(12 citation statements)

References 52 publications

(90 reference statements)

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“…For example, experiments have identified EPA as a strong predictor of growth in cladoceran zooplankton [ 23 , 24 ], and isopods [ 25 ]. Increased dietary arachidonic ARA correlates with improved growth in juvenile bivalves [ 26 ], gonad development in sea urchins [ 27 – 29 ], and higher fecundity in marine copepods [ 30 ]. DHA is critical to fish larval development [ 31 – 33 ], and copepod egg viability [ 34 ], and egg-production rates [ 35 ].…”

Section: Introductionmentioning

confidence: 99%

Partitioning the Relative Importance of Phylogeny and Environmental Conditions on Phytoplankton Fatty Acids

2015

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Essential fatty acids (EFA), which are primarily generated by phytoplankton, limit growth and reproduction in diverse heterotrophs. The biochemical composition of phytoplankton is well-known to be governed both by phylogeny and environmental conditions. Nutrients, light, salinity, and temperature all affect both phytoplankton growth and fatty acid composition. However, the relative importance of taxonomy and environment on algal fatty acid content has yet to be comparatively quantified, thus inhibiting predictions of changes to phytoplankton food quality in response to global environmental change. We compiled 1145 published marine and freshwater phytoplankton fatty acid profiles, consisting of 208 species from six major taxonomic groups, cultured in a wide range of environmental conditions, and used a multivariate distance-based linear model to quantify the total variation explained by each variable. Our results show that taxonomic group accounts for 3-4 times more variation in phytoplankton fatty acids than the most important growth condition variables. The results underscore that environmental conditions clearly affect phytoplankton fatty acid profiles, but also show that conditions account for relatively low variation compared to phylogeny. This suggests that the underlying mechanism determining basal food quality in aquatic habitats is primarily phytoplankton community composition, and allows for prediction of environmental-scale EFA dynamics based on phytoplankton community data. We used the compiled dataset to calculate seasonal dynamics of long-chain EFA (LCEFA; ≥C20 ɷ-3 and ɷ-6 polyunsaturated fatty acid) concentrations and ɷ-3:ɷ-6 EFA ratios in Lake Washington using a multi-decadal phytoplankton community time series. These analyses quantify temporal dynamics of algal-derived LCEFA and food quality in a freshwater ecosystem that has undergone large community changes as a result of shifting resource management practices, highlighting diatoms, cryptophytes and dinoflagellates as key sources of LCEFA. Moreover, the analyses indicate that future shifts towards cyanobacteria-dominated communities will result in lower LCEFA content in aquatic ecosystems.

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Section: Introductionmentioning

confidence: 99%

Partitioning the Relative Importance of Phylogeny and Environmental Conditions on Phytoplankton Fatty Acids

2015

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“…Past feeding experiments with S. droebachiensis have shown, for example, that they have considerable ability to modify their dietary FA over long experiments (14 week duration; Kelly et al, 2008), or that they do not incorporate their dietary FA signal into their tissues in very short experiments (3 week duration; Wessels et al, 2012). A long (17 week) feeding experiment with adult red urchins (Mesocentrotus franciscanus) showed that urchin FAs were strongly differentiated in the gonad tissues of urchins fed two kelp species (Raymond et al, 2014). Our results show that when fed for a sufficiently long period (e.g., 25 weeks in S. droebachiensis, 10 weeks in S. purpuratus), both urchins' multivariate FA compositions are strongly affected by their diets; in fact, both species can be differentiated based on whether they were fed brown, red, and green algae (NMDS and PERMANOVA results).…”

Section: Discussionmentioning

confidence: 99%

“…Despite these differences, particularly between urchin species and life stage, it is nonetheless clear that growing urchins, whether from increased tissue biomass, or in gonad development, incorporated multivariate FA profiles of the algae provided. The macroalgal diets selected here are known to have strong differences in their FA; future work could investigate whether it is possible to trace the FA of more closely related algae, e.g., different species of Laminariales (e.g., Raymond et al, 2014), into these urchin species.…”

Section: Discussionmentioning

confidence: 99%

“…Macroalgae were maintained in ambient flow-through seawater tables in the lab prior to presentation to urchins. No macroalgae were kept for longer than 1 week, as aging has been shown to affect kelp FA (Raymond et al, 2014). To prepare macroalgae, thalli were rinsed briefly in freshwater to dislodge mobile epibionts, e.g.…”

Section: Strongylocentrotus Purpuratus Feeding Assaysmentioning

confidence: 99%

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Trophic Transfer of Macroalgal Fatty Acids in Two Urchin Species: Digestion, Egestion, and Tissue Building

et al. 2018

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Sea urchins are ecosystem engineers of nearshore benthic communities because of their influence on the abundance and distribution of macroalgal species. Urchins are notoriously inefficient in assimilation of their macroalgal diets, so their fecal production can provide a nutritional subsidy to benthic consumers that cannot capture and handle large macroalgae. We studied the assimilation of macroalgal diets by urchins by analyzing the profiles of trophic biomarkers such as fatty acids (FAs). We tracked macroalgal diet assimilation in both Strongylocentrotus droebachiensis and S. purpuratus. Juvenile S. droebachiensis and adult S. purpuratus were maintained for 180 and 70 days, respectively, on one of three monoculture diets from three algal phyla: Nereocystis luetkeana, Pyropia sp., or Ulva sp. We then analyzed FA profiles of the macroalgal tissue fed to urchins as well as urchin gonad, gut, digesta, and egesta (feces) to directly evaluate trophic modification and compare nutritional quality of urchin food sources, urchin tissues, and fecal subsidies. In the S. purpuratus assay, there were significantly more total lipids in the digesta and egesta than in the algae consumed. The FA profiles of urchin tissues differed among urchin species, all diets, and tissue types. Despite these differences, we observed similar patterns in the relationships between the urchin and macroalgal tissues for both species. Egesta produced by urchins fed each of the three diets were depleted with respect to the concentration of important long chain polyunsaturated fatty acids (LCPUFAs), but did not differ significantly from the source alga consumed. Both urchin species were shown to synthesize and selectively retain both the precursor and resulting LCPUFAs involved in the synthesis of the LCPUFAs 20:4ω6 and 20:5ω3. S. droebachiensis and S. purpuratus exhibited consistent patterns in the respective depletion and retention of precursor FAs and resulting LCPUFAs of Pyropia and Ulva tissues, suggesting species level control of macroalgal digestion or differential tissue processing by gut microbiota. For both S. droebachiensis and S. purpuratus, macroalgal diet was a surprisingly strong driver of urchin tissue fatty acids; this indicates the potential of fatty acids for future quantitative trophic estimates of urchin assimilation of algal phyla in natural settings.

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“…I collected fresh N. luetkeana from kelp beds in the San Juan Channel on the day of the experiment. To simulate detached drift bull kelp, I aged non-reproductive blades in a black-plastic covered outdoor tank with flowing seawater for one week prior to the feeding experiment ( Raymond, Lowe & Galloway, 2014 ). As in the other electivity experiments, each crab was offered an approximately 10 × 30 cm piece of fresh (mean mass ± SE = 17.6 ± 1.4 g) and aged bull kelp (mean mass ± SE = 21.3 g ± 1.6 g) in a choice experiment.…”

Section: Methodsmentioning

confidence: 99%

The role of kelp crabs as consumers in bull kelp forests—evidence from laboratory feeding trials and field enclosures

Dobkowski

2017

PeerJ

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The Northern kelp crab (Pugettia producta) and the graceful kelp crab (Pugettia gracilis) are common primary consumers in bull kelp beds near the San Juan Islands (Salish Sea, NE Pacific). In this system, urchins (often considered the most voracious herbivores exerting top-down control on kelp beds) tend to remain sedentary because of the high availability of detrital macroalgae, but the extent to which kelp crabs consume kelp (and other food options) is largely unknown. I conducted four types of laboratory feeding experiments to evaluate kelp crab feeding patterns: (1) feeding electivity between bull kelp (Nereocystis luetkeana) and seven species of co-occurring local macroalgae; (2) feeding electivity on aged vs. fresh bull kelp; (3) feeding preference between N. luetkeana and small snails (Lacuna sp.); and (4) scaling of feeding rate with body size in P. producta and P. gracilis. In choice experiments, P. producta consumed greater mass of N. luetkeana than of other macroalgal species offered and elected to eat fresh bull kelp over aged. However, P. producta also consumed snails (Lacuna sp.), indicating more generalized feeding than previously suspected. Feeding rates for P. producta exceeded the expected 3∕4 scaling rule of metabolic rates, indicating that larger P. producta may have a disproportionately large impact on bull kelp. A subtidal field experiment, designed to assess the influence of consumers on juvenile bull kelp net tissue gain, found that only fully enclosed (protected) bull kelp increased in wet mass and blade length. Herbivory by kelp crabs, among other consumers, is likely to play a previously unrecognized role in mediating the growth and survival of this annual kelp species within the Salish Sea.

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Degradation state of algal diets affects fatty acid composition but not size of red urchin gonads

Cited by 10 publications

References 52 publications

Partitioning the Relative Importance of Phylogeny and Environmental Conditions on Phytoplankton Fatty Acids

Partitioning the Relative Importance of Phylogeny and Environmental Conditions on Phytoplankton Fatty Acids

Trophic Transfer of Macroalgal Fatty Acids in Two Urchin Species: Digestion, Egestion, and Tissue Building

The role of kelp crabs as consumers in bull kelp forests—evidence from laboratory feeding trials and field enclosures

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