Evaluating the Impact of the Invasive Kelp Undaria Pinnatifida on Native California Kelps Egregia Menziesii and Macrocystis Pyrifera PDF Download

Author: Marla Elaine Ranelletti
Publisher:
ISBN:
Category :
Languages : en
Pages : 200

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Author:
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ISBN:
Category : Electronic books
Languages : en
Pages : 40

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Invasive species can alter patterns of abundance and diversity in species that are ecosystem engineers, which in turn may impact the ecosystem services these species provide. This study addresses how the recent invasion of the brown algae, Sargassum horneri, alters native algal abundances and rates of primary production on Catalina Island, California, USA. Specifically, I identified what drove diurnal patterns of Gross Primary Production (GPP) and Net Primary Production (NPP) in benthic algal communities on a subtidal rocky reef on Catalina Island that had been invaded by S. horneri. Additionally, I conducted periodic S. horneri removals to examine how S. horneri removal may influence native algal abundances, GPP and NPP. My study revealed that variation in morning GPP among months is driven primarily by changes in S. horneri biomass. In contrast, variation in afternoon GPP among months is primarily driven by differences in ocean temperature. Daily variations in GPP is strongly influenced by changes in temperature, algal metabolism and light conditions, ultimately resulting in net respiration by late afternoon. Moreover, S. horneri removal led to 9x more adult giant kelp stipes, Macrocystis pyrifera and 3x more juvenile kelps ( Ecklonia arborea and M. pyrifera) in S. horneri removal plots than in control plots. However, these changes in algal abundances upon S. horneri removal did not scale up to drive significant changes in GPP or NPP among treatments over the course of this study, suggesting that S. horneri removals may need to be conducted for more than a year to see significant changes in primary production. This study provides evidence that the invasion of S. horneri negatively alters patterns of native algae abundance and primary production on subtidal rocky reefs at Catalina Island.

Author: Michael S. Foster
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ISBN:
Category : Giant kelp
Languages : en
Pages : 184

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Author: Wheeler J. North
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ISBN:
Category : Science
Languages : en
Pages : 634

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Author: Rocío Suárez Jiménez
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ISBN:
Category : Aquatic ecology
Languages : en
Pages : 189

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Finally, field studies revealed that U. pinnatifida provides a comparable habitat to the also morphologically simple macroalgae Xiphophora gladiata and Marginariella spp., but hosts only 1/4 of the density of invertebrates compared to morphologically complex species such as Carpophyllum spp., Cystophora spp. and Sargassum sinclarii. The findings reveal that the role of U. pinnatifida as a habitat and food for the native fauna varies across ecosystems and among invertebrate species but is was generally similar to some of the native macroalgae it was compared to. This work has also demonstrated that knowledge of traits specific to faunal species (i.e. trophic position, habitat use, etc.) and macroalgae (i.e. chemistry, biomechanics, morphology, etc.) need to be considered when predicting the effects of invasive species.

Author: Kate James
Publisher:
ISBN:
Category : Invasive plants
Languages : en
Pages : 127

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Macroalgal invasions can change the structure and function of benthic habitat, dominating space, altering primary productivity, nutrient cycles, and community composition. This is a serious concern for receiving environments. A major determinant of the geographic distribution of macroalgal species is water temperature. Investigating the population ecology, genetic variation and factors controlling the density and spread of invasive macroalgae towards the extent of their thermal distribution limits can therefore provide important insights into the potential range and ecological impacts both now and with future climate change. The kelp Undaria pinnatifida is a prolific and cosmopolitan invasive species. Undaria has invaded countries around the world across a variety of temperature regimes. Undaria displays a variable phenology at introduced locations; it is a winter annual in its native range, but sporophyte presence can vary from annual to year-round across its invasive range. Information is lacking on how Undaria phenology and impacts manifest under warm-temperate conditions. This work studies Undaria in northern New Zealand, one of the warmest-water populations in the world. I investigated how water temperature influenced the phenology and distribution of Undaria. In addition I examined some attributes of the invasion process for warm-water populations; I looked at the role mussel aquaculture plays in influencing the spread of Undaria to native habitats, how disturbance might facilitate the spread of Undaria to subtidal reefs, and the genetic composition of populations in northern New Zealand. Monitoring over three growth seasons revealed how Undaria in northern New Zealand displayed an annual growth cycle. Recruitment occurred when temperatures dropped below ~15 oC and density was minimal at temperatures above 20 oC. Sporophyte size and growth rates were comparable to those of cooler water populations but the seasonal cycle was compressed into a shorter timeframe. Undaria was found to proliferate on mussel farms and low numbers were found on reefs adjacent to farms, in shallow habitats lacking native macroalgal canopies. Undaria was rare in deeper habitats dominated by native macroalgal canopies, experimental canopy removal did not facilitate the spread of Undaria into these habitats at the site examined. This suggests that native canopy-forming species are not the sole factor prohibiting the invasion of Undaria to subtidal reef sites in this region. Genetic analysis of Undaria from all known populations in the North Island revealed very low genetic diversity in northern New Zealand. The presence of a single haplotype in northeastern New Zealand may indicate a particularly warm-tolerant strain and suggests thermal preadaptation may influence invasion success. An investigation into the global distribution and associated phenology of Undaria, and how this related to water temperature regimes, demonstrated how Undaria only occurred where winter temperatures dropped below ~15 oC and that persistent year-round populations were only present at sites where summer temperatures did not exceed 20 oC. This analysis also revealed that there are extensive areas of the world where Undaria does not occur that have temperature regimes suitable for Undaria colonisation. Such areas are potentially at risk from future invasion based on current temperature regimes. These thermal limits for Undaria indicate that populations in northern New Zealand are towards the limit of its distribution, with winter temperatures close to 15 oC, Undaria is unable to withstand warmer winter temperatures. Ocean warming is likely to restrict the potential geographic distribution of Undaria, particularly where winter temperatures exceed 15 oC. Increases in summer temperatures, which prolong the period during the year when temperatures exceed 20 oC, will reduce the annual persistence of Undaria. A limited annual presence of sporophytes at warmer locations may reduce the ecological impacts of Undaria invasion as compared to cooler water locations where sporophytes persist for a longer portion of the year.

Author: Inger Wallentinus
Publisher:
ISBN:
Category : Biodiversity conservation
Languages : en
Pages : 46

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Author: Samuel Charles Ginther
Publisher:
ISBN:
Category :
Languages : en
Pages : 85

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The susceptibility of ecosystems to the introduction of non-native species has increased drastically with the development of advanced transportation technologies. It is now quite common for organisms to be easily transported by humans across physiological, ecological, or behavioral barriers that once served as natural population constraints. Despite this increased rate of introductions to locations that were previously unreachable, most organisms that are introduced perish because they are not able to withstand the new environmental pressures of the introduced location, or there are simply not enough conspecifics to perpetuate the population. However, when introduced organisms are able to thrive and reproduce, they may have devastating economic or ecological consequences. A new opportunity to document and understand the effects of an invasive alga on native community members has presented itself in southern Californian waters. Native to northeastern Asia, Sargassum horneri is a macroalga that was presumably transported in ballast water and discovered in Long Beach Harbor in 2003. By 2006 it had spread to the western side of Santa Catalina Island, California, and within a year spread along the entire leeward coast, forming dense stands in numerous areas. Although not all exotic species are ecologically harmful, S. horneri has attributes (fast growing and occurs in high densities) that may allow it to readily establish and out compete marine flora critical to the community structure of fishes. The purpose of this study aimed to document the effects of S. horneri on kelp forest fishes at Santa Catalina Island, California. I first employed observational, correlative methods to explore the role of S. horneri in shaping biotic and abiotic habitat characteristics of reefs and fish assemblages. I also explored habitat characteristics that predict fish assemblage structure, as well as species-specific responses of fish to habitat predictor variables during 4 distinct time periods. Fish assemblages changed over the course of my 4 sampling periods, and a number of habitat variables (including S. horneri) explained variation in fish assemblage during those times. However, there is more evidence that favors M. pyrifera as a driver of fish assemblage change, as indicated by species-level responses. Additionally, a field experiment testing whether the removal of S. horneri from reef areas affected the fish assemblage was used to evaluate whether patterns documented in the observational portion of my study that could be attributed to S. horneri do in fact appear to be caused by the invasive alga. Removing S. horneri from established areas of reef did not affect multivariate or univariate metrics of fish assemblage over the course of 7 sampling periods. Removal and control (unaltered) areas of reef contained strikingly similar fish assemblages, fish richness, and fish densities over time. Despite a drastic change in reef landscape, it appears that M. pyrifera, rather than S. horneri, was a more significant driver of differences in kelp forest fish assemblages observed in my study. Second, I compared the role of relatively low-lying S. horneri and vertically extensive M. pyrifera in shaping recruitment patterns of a popular sport fish (Paralabrax clathratus) by using an observational and experimental study. I first examined kelp bass recruit abundance on naturally standing S. horneri and M. pyrfera to better understand how fish recruitment rates differ between the introduced and native species. Additionally, I experimentally isolated 3 treatments (M. pyrifera only, S. horneri only, and M. pyrifera and S. horneri together) over a sandy bottom to understand whether the presence of S. horneri, and increased benthic complexity for young fish, enhances kelp bass recruitment. An overwhelming majority of kelp bass recruited to M. pyrifera, and larger recruits were located in the bottom two-thirds of the thalli. Kelp bass recruitment was were observed with S. horneri, regardless of whether the alga was alone or paired with M. pyrifera. Similar to my observational results, larger kelp bass recruits were observed in the bottom third of M. pyrifera treatments. Additionally, I found that the presence of larger, predatory conspecifics explained a spatial pattern of declining recruitment rates across treatment plots. My study presents the first evidence that S. horneri negatively impacts the recruitment of an important southern California reef fish. Results from both of my studies offer contrasting outlooks on S. horneri's role in southern California kelp forests. When focusing on the entire fish assemblage, little evidence is in favor of S. horneri as a driver of kelp forest fish structure. However when focusing on a particular early life history characteristic of a common kelp forest fish, the effects of S. horneri are dramatically negative. The contrasting results of my studies are important reminders for the need of additional studies to generate a more comprehensive understanding of this invasive alga's impact on kelp forest organisms.

Author: Steven Ryan Cunningham
Publisher:
ISBN:
Category : Giant kelp
Languages : en
Pages : 110

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Author: Robert Scott Kimura
Publisher:
ISBN:
Category : Giant kelp
Languages : en
Pages : 252

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