Functional properties of the isomorphic biphasic algal life cycle

Many species of marine algae have life cycles that involve multiple separate, free-living phases that frequently differ in ploidy levels. These complex life cycles have received increasing scientific attention over the past few decades, due to their usefulness for both ecological and evolutionary studies. I present a synthesis of our current knowledge of the ecological functioning and evolutionary implications of the isomorphic, biphasic life cycles commonly found in many species of marine algae. There are both costs and benefits to life cycles with 2 morphologically similar but separate, free-living phases that differ in ploidy levels (haploids and diploids). Evolutionary theory predicts that the existence of subtle yet important differences between the phases may be what allows these life cycles to be maintained. Different phases of the same species can vary in abundance, in demographic parameters such as mortality and fecundity, in their physiology, and in their resistance to herbivory. Some taxonomic groups within the red algae have received significant attention toward these issues, while our knowledge of these properties for brown and green algae remains limited

Herbivore Impacts on the Invasive Marine Alga Grateloupia turuturu

Invasive species have the ability to outcompete natives, and can create a monoculture if not mitigated by herbivores or some other mechanism. Limited information exists on the ecology of the invasive macroalga Grateloupia turuturu and how it is impacted by herbivores. Using laboratory mesocosm experiments, we investigated the ability of two invasive herbivore species common in Rhode Island, the snail Littorina littorea and Asian shore crab Hemigrapsus sanguineus, to control Grateloupia populations. In the first trial, Grateloupia was provided to a single herbivore (either Littorina or Hemigrapsus) or both herbivores together. Grateloupia controls were in the same mesocosms as each treatment, but were separated by a mesh partition to allow water flow and account for possible facilitation by herbivore presence. Mesocosms were kept at 13°C and at 0, 2, 4, and 6 days, the algae was weighed and water samples were taken. Preliminary results indicate that Littorina do indeed graze on Grateloupia, with an average decrease in mass of 44.6% after 6 days. There was no significant change in mass of Grateloupia in the presence of Hemigrapsus only or with Littorina and Hemigrapsus together. Future trials will include two common species of marine macroalgae along with the Grateloupia, to investigate herbivore feeding preference when exposed to multiple food choices. The ultimate results of these trials are intended to indicate the success of the continued invasion of Grateloupia in Rhode Island waters, and predict the role of invasive herbivores in controlling Grateloupia populations

Examination of \u3cem\u3eUlva\u3c/em\u3e bloom species richness and relative abundance reveals two cryptically co- occurring bloom species in Narragansett Bay, Rhode Island

Blooms caused by the green macroalga Ulva pose a serious threat to coastal ecosystem 20 around the world. Despite numerous studies of the causes and consequences of these blooms, we still have a limited understanding of Ulva bloom species richness and abundance due to difficulties in identifying Ulva species using morphological features. Along the northeastern U.S. coastline, all blooms of distromatic Ulva blades were previously identified as U. lactuca. Recent molecular sequencing, however, discovered the presence of additional distromatic Ulva species. Therefore, in order to determine the relative abundance of Ulva species within blooms, we conducted monthly surveys at four Narragansett Bay, RI, sites representing a gradient of bloom severity. We found that the biomass of Ulva within blooms was a mix of U. compressa and U. rigida, not U. lactuca as previously reported. In contrast, sites not impacted by blooms that were located near the mouth of Narragansett Bay were dominated by U. lactuca. We also observed spatial and temporal differences in Ulva and total macroalgal diversity between bloom-impacted sites, indicating that Ulva bloom composition can be radically different between similar sites within close proximity. We discuss our results in the context of Ulva blooms worldwide, highlighting the need to definitively determine bloom species composition in order to fully understand bloom dynamics

Utilization of the Invasive Alga Gracilaria Vermiculophylla (Ohmi) Papenfuss by the Native Mud Snail Ilyanassa Obsoleta (Say)

The recent invasions of the red alga, Gracilaria vermiculophylla, to the Atlantic and Eastern Pacific Oceans have the potential to significantly alter intertidal and subtidal soft sediment communities. In particular, G. vermiculophylla increases habitat complexity and provides a novel hard substrate in an otherwise two dimensional habitat. Following our observations that the native omnivorous mud snail Ilyanassa obsoleta utilizes G. vermiculophylla for egg capsule deposition, our field surveys demonstrated that the in situ abundance of egg capsules on G. vermiculophylla matched abundances on a native alga Ceramium virgatumandwere at least 11–50 times greater than on all other co-occurring macrophytes. Additionally, through mesocosm experiments, we showed that I. obsoleta preferentially deposits eggs on the invasive G. vermiculophylla over native substrates. However, despite the thick layer of egg capsules found on G. vermiculophylla, no detrimental effects were seen on thalli growth. In contrast, growth of the native red alga Ceramium virgatum was significantly reduced when egg capsules were present, suggesting G. vermiculophylla can out-compete native macrophytes in areas of I. obsoleta abundance, while facilitating reproduction of the native mud snail. This novel interaction has the potential to significantly alter biological interactions in soft sediment communities through a variety of different mechanisms, including the alteration of trophic cascades via the increase in mud snail abundance. Furthermore, facilitation of the reproductive success of I. obsoleta may lead to increases in the occurrence of cercarial dermatitis, as I. obsoleta is a known intermediate host organism

Snail Grazing Facilitates Growth of a Bloom-Forming Alga

Herbivory often has a negative effect on plants. However, there is a growing number of examples, primarily in terrestrial ecosystems, where herbivory causes an increase in plant size, growth rate, and/or reproductive output. In marine ecosystems, the positive effects of herbivores on macroalgae are not as well studied, although limited evidence exists for herbivore-induced increases in macroalgal growth rates via 2 mechanisms: nutrient addition via grazer defecation, and epiphyte removal. In this study, we examined the effects of grazing by the mud snail Ilyanassa obsoleta on Ulva lactuca, the dominant bloom-forming macroalga in many New England estuaries. We found that the presence of I. obsoleta had a significant positive, rather than negative, effect on U. lactuca. Through caging experiments, we established that this positive effect was not due to fecal nutrient inputs from the snail. Similarly, snail contact in the absence of grazing did not affect U. lactuca growth rates. In contrast, grazing by I. obsoleta significantly reduced the microalgal cover on heavily fouled U. lactuca blades, indicating that snail herbivory of microalgal films likely facilitates U. lactuca growth. Our study demonstrates the surprising, positive effect that an abundant herbivore can have on the growth of a macroalgal bloom species

Herbivore Impacts on Two Morphologically Similar Bloom-Forming Ulva Species in a Eutrophic Bay

Herbivore impacts on macrophyte growth vary with the identity of the herbivores and macrophytes, as well as under different abiotic conditions. This interaction is further complicated by anthropogenic alterations to the environment, such as eutrophication. In this study, we utilized in situ herbivore exclusion experiments and mesocosm feeding preference assays to examine the impacts of different herbivores on the growth of two morphologically similar, co-occurring macroalgal bloom Ulva species in a nutrient-rich environment. We found that herbivory had a measurable impact on Ulva biomass, though the rate of consumption rarely surpassed growth for either Ulva species. We determined that the primary herbivores within the blooms were amphipods and mud crabs, and that their effects varied among study sites and months. Our results also confirmed that, even with a diverse suite of consumers, Ulva blooms are capable of escaping herbivore control, particularly early in the growing season when growth rates peak and herbivore activity is limited. Furthermore, our experiments revealed species-specific feeding preferences among herbivores, as well as differences in growth rates and chemistry between the two Ulva species, which likely influence bloom dynamics

Chemical Warfare in Narragansett Bay: Determining the Allelopathic Effects of Ulva

Several species of Ulva are commonly found in the waters of Narragansett Bay, especially in eutrophic waters, where they can form fast growing blooms that can have ecological and economic consequences. The formation and release of allelopathic chemicals has been previously documented in some species of Ulva, including Ulva lactuca. Three species of blade-forming Ulva are commonly found in Narragansett Bay and coastal Rhode Island, namely, U. compressa, U. lactuca, and U. rigida. We aimed to determine if these three species of Ulva had allelopathic effects by testing their impacts on the growth of other macroalgae. Cystoclonium purpureum, Chondrus crispus, and Ceramium virgatum tips were grown alone (control) or with either U. compressa, U. rigida, or U. lactuca in mesocosms separated by mesh for eight days, in two separate trials. The blotted-dry fresh weight of Cystoclonium, Chondrus, and Ceramium was recorded every other day and tips were photographed for surface area analysis. Nutrients were checked daily using NO3 as a proxy and adjusted to prevent nutrient limitation. All three species of Ulva had a significant negative effect on the growth of Cystoclonium, Chondrus, and Ceramium, although the effect was dependent on time. In the Cystoclonium trial, U. compressa and U. rigida treatments had the largest negative effect on Cystoclonium growth with overall mass loss observed after 6 days of co-culture. U. lactuca had a smaller negative effect on growth, with the average Cystoclonium growth rate after 8 days of co-culture (2.9 ± 0.9 % day-1) significantly below controls (5.0 ± 0.8 % day-1). In the Chondrus trial, there was a striking effect of all three Ulva species on the growth of Chondrus after only two days of co-culture. Growth rates of tips with all species of Ulva were \u3c1% day-1 for the duration of the experiment, while the control tips increased in growth over time from 1.83 (± 0.7) % day-1 on Day 2 to 5.56 (± 0.9) % day-1 on Day 8. Overall mass loss was observed after 8 days of co-culture with U. compressa. The Ceramium growth was more variable over the course of the trial, but clear separation was seen on day 8 between the controls and the decreased growth of the tips co-cultured with Ulva. All three species of Ulva had a similar effect on the growth of Ceramium at the end of the trial. Our results indicate that U. compressa, U. lactuca, and U. rigida can significantly inhibit the growth of other macroalgae. This has implications for secondary effects of Ulva blooms reducing the algal diversity in addition to primary effects of eutrophication

The brown macroalga Colpomenia peregrina (Sauvageau, 1927) reaches Rhode Island, USA

Introduced, or nonnative, marine species are a threat to local biodiversity, disrupt marine industries, and can have negative effects on coastal communities. Colpomenia peregrina (Sauvageau, 1927) is one of the most successful brown algal invaders in the world. Originating from the Northwest Pacific, Colpomenia peregrina was first collected in the Northwest Atlantic in Nova Scotia, Canada in the 1960s. Since then populations of C. peregrina have been discovered at 57 sites ranging from Grand Barachois Lagoon, Saint Pierre and Miquelon to South Wellfleet, MA, USA. The spread of Colpomenia peregrina can be attributed to its broad tolerance to environmental conditions, buoyant morphology that aids dispersal, and generalist epiphytic biology. Here we report the occurrence of Colpomenia peregrina at five sites in Rhode Island, USA for the first time, representing the crossing of a major biogeographic boundary by this species. The spread of C. peregrina will likely continue, warranting research on its impact on native communities and host algae

Implementing adaptive management into a climate change adaptation strategy for a drowning New England salt marsh

Due to climate change and other anthropogenic stressors, future conditions and impacts facing coastal habitats are unclear to coastal resource managers. Adaptive management strategies have become an important tactic to compensate for the unknown environmental conditions that coastal managers and restoration ecologists face. Adaptive management requires extensive planning and resources, which can act as barriers to achieve a successful project. These barriers also create challenges in incorporating adaptive management into climate change adaptation strategies. This case study describes and analyzes the Rhode Island Coastal Resources Management Council\u27s approach to overcome these challenges to implement a successful adaptive management project to restore a drowning salt marsh using the climate change adaptation strategy, sediment enhancement, at Quonochontaug Pond in Charlestown, RI. Through effective communication and active stakeholder involvement, this project successfully incorporated interdisciplinary partner and stakeholder collaborations and developed an iterative learning strategy that highlights the adaptive management method

THE INFLUENCE OF SALT MARSH FUCOID ALGAE (ECADS) ON SEDIMENT DYNAMICS OF NORTHWEST ATLANTIC MARSHES

Resilience is currently a key theme within salt marsh ecological studies. Understanding the factors that affect salt marsh accretion and elevation gains are of paramount importance if management of these ecosystems is to be successful under increasing synergistic stresses of storm surge, inundation period, and eutrophication. We present the results of salt marsh fucoid algae (ecads) removal experiments on Spartina alterniflora abundance, production and decomposition and the sedimentary dynamics of two marshes on Cape Cod, Massachusetts. The presence of the thick layer of marsh fucoids had a significant and positive influence on sediment deposition, accretion, concentration of water column particulates, while it inhibited water flow. Decomposition rates of Spartina alterniflora in the field were significantly higher under the fucoid macroalgae layer, and, in lab experiments, S. alterniflora seedlings added more leaves when the marsh fucoids were present. In contrast, fucoids caused a significant decrease in S. alterniflora seedlings’ survival in the field. We found that marsh fucoids are stable despite not being attached to any substrate, and field surveys revealed a relatively widespread, but not ubiquitous, distribution along outer Cape Cod. Salt marsh fucoid algae directly and substantially contribute to salt marsh sediment elevation gain, yet their potential inhibitory effects on colonizing S. alterniflora may counteract some of their overall contributions to salt marsh persistence and resilience