Ecological Effects of Undaria pinnatifida (Harvey) Suringar and Nutrient-Enrichment on Intertidal Assemblages in the Wellington Region of New Zealand

<p>The introduction of non-native species and the alteration of seawater nutrient regimes due to anthropogenic impacts are two important threats to marine environments. Moreover, these disturbances may interact in such a way that promotes the success of invasive species in coastal habitats. This thesis contributes to current gaps in knowledge in these areas for low-intertidal communities. Algal community dynamics and ecological effects of the invasive kelp Undaria pinnatifida on low shores in the Wellington region, New Zealand, were examined, using field surveys and experiments. In addition, the role of variability in nutrient concentrations in coastal waters in mediating algal community structure and diversity, and the success of U. pinnatifida reproduction were investigated. Algal surveys were used in two locations thought to differ in nutrient regimes, the Wellington Harbour and the Wellington south coast, to explore the structure and dynamics of algal assemblages. Results showed high variability of low-intertidal algal communities among sites, but no consistent differences in algal community composition were found between the two locations, despite higher U. pinnatifida cover in the harbour. Over the duration of the study, nutrient regimes did not differ greatly between the locations. The response of rocky intertidal algal assemblages to chronic exposure to high nutrient effluent was investigated using two nearshore sewage outfalls in the Wellington region. The Titahi Bay outfall showed a stronger relationship between nutrients and algal community composition. Variation in algal assemblage structure and diversity was best explained by phosphate concentrations. By contrast, at the more wave-exposed Pencarrow outfall, patterns of change in the algal community were less clear and there was a much weaker relationship with seawater nutrients. Because removal of native algal canopy species may facilitate the establishment of invasive macroalgae, the invasion process of U. pinnatifida in disturbed patches in a rocky low-intertidal habitat was investigated. In a site where U. pinnatifida had not yet established, patches were scraped clear of native algal cover at two different times of year, and recruitment of U. pinnatifida was monitored. While U. pinnatifida invaded the site, it recruited in control plots at a similar rate as cleared plots, suggesting that physical disturbance of the native algal assemblage is not a key requirement for this kelp to invade and establish in new areas in the low intertidal zone. The response of native algal assemblages to removal of U. pinnatifida individuals was investigated at intertidal sites in the Wellington Harbour and on the south coast. No significant effect of U. pinnatifida on community composition, diversity, and species richness was detected. Removal of this invader did not change native intertidal assemblage structure in either harbour or south coast sites. Lastly, effects of different nutrient regimes and light intensities on early development and reproduction of U. pinnatifida were studied using a laboratory experiment. Under low light conditions U. pinnatifida gametophyte growth and reproduction stalled and was not increased by the addition of nutrients. However, at medium and high light levels, gametophyte growth and reproduction, and particularly early stage sporophyte growth rates increased when exposed to higher nutrient concentrations.These effects could have implications for U. pinnatifida population dynamics in intertidal habitats where light is not often a limiting resource. This research contributed to a better understanding of factors that underlie invasion dynamics, distribution, and ecological effects of U. pinnatifida and seawater nutrient regimes on low-intertidal assemblages in the Wellington region. The outcomes can assist in setting up strategic environmental protection and conservation plans.</p>

Ecological Effects of Undaria pinnatifida (Harvey) Suringar and Nutrient-Enrichment on Intertidal Assemblages in the Wellington Region of New Zealand

<p>The introduction of non-native species and the alteration of seawater nutrient regimes due to anthropogenic impacts are two important threats to marine environments. Moreover, these disturbances may interact in such a way that promotes the success of invasive species in coastal habitats. This thesis contributes to current gaps in knowledge in these areas for low-intertidal communities. Algal community dynamics and ecological effects of the invasive kelp Undaria pinnatifida on low shores in the Wellington region, New Zealand, were examined, using field surveys and experiments. In addition, the role of variability in nutrient concentrations in coastal waters in mediating algal community structure and diversity, and the success of U. pinnatifida reproduction were investigated. Algal surveys were used in two locations thought to differ in nutrient regimes, the Wellington Harbour and the Wellington south coast, to explore the structure and dynamics of algal assemblages. Results showed high variability of low-intertidal algal communities among sites, but no consistent differences in algal community composition were found between the two locations, despite higher U. pinnatifida cover in the harbour. Over the duration of the study, nutrient regimes did not differ greatly between the locations. The response of rocky intertidal algal assemblages to chronic exposure to high nutrient effluent was investigated using two nearshore sewage outfalls in the Wellington region. The Titahi Bay outfall showed a stronger relationship between nutrients and algal community composition. Variation in algal assemblage structure and diversity was best explained by phosphate concentrations. By contrast, at the more wave-exposed Pencarrow outfall, patterns of change in the algal community were less clear and there was a much weaker relationship with seawater nutrients. Because removal of native algal canopy species may facilitate the establishment of invasive macroalgae, the invasion process of U. pinnatifida in disturbed patches in a rocky low-intertidal habitat was investigated. In a site where U. pinnatifida had not yet established, patches were scraped clear of native algal cover at two different times of year, and recruitment of U. pinnatifida was monitored. While U. pinnatifida invaded the site, it recruited in control plots at a similar rate as cleared plots, suggesting that physical disturbance of the native algal assemblage is not a key requirement for this kelp to invade and establish in new areas in the low intertidal zone. The response of native algal assemblages to removal of U. pinnatifida individuals was investigated at intertidal sites in the Wellington Harbour and on the south coast. No significant effect of U. pinnatifida on community composition, diversity, and species richness was detected. Removal of this invader did not change native intertidal assemblage structure in either harbour or south coast sites. Lastly, effects of different nutrient regimes and light intensities on early development and reproduction of U. pinnatifida were studied using a laboratory experiment. Under low light conditions U. pinnatifida gametophyte growth and reproduction stalled and was not increased by the addition of nutrients. However, at medium and high light levels, gametophyte growth and reproduction, and particularly early stage sporophyte growth rates increased when exposed to higher nutrient concentrations.These effects could have implications for U. pinnatifida population dynamics in intertidal habitats where light is not often a limiting resource. This research contributed to a better understanding of factors that underlie invasion dynamics, distribution, and ecological effects of U. pinnatifida and seawater nutrient regimes on low-intertidal assemblages in the Wellington region. The outcomes can assist in setting up strategic environmental protection and conservation plans.</p>

Macro-Nutrient Stoichiometry of Glacier Algae From the Southwestern Margin of the Greenland Ice Sheet

Glacier algae residing within the surface ice of glaciers and ice sheets play globally significant roles in biogeochemical cycling, albedo feedbacks, and melt of the world’s cryosphere. Here, we present an assessment of the macro-nutrient stoichiometry of glacier algal assemblages from the southwestern Greenland Ice Sheet (GrIS) margin, where widespread glacier algal blooms proliferate during summer melt seasons. Samples taken during the mid-2019 ablation season revealed overall lower cellular carbon (C), nitrogen (N), and phosphorus (P) content than predicted by standard microalgal cellular content:biovolume relationships, and elevated C:N and C:P ratios in all cases, with an overall estimated C:N:P of 1,997:73:1. We interpret lower cellular macro-nutrient content and elevated C:N and C:P ratios to reflect adaptation of glacier algal assemblages to their characteristic oligotrophic surface ice environment. Such lower macro-nutrient requirements would aid the proliferation of blooms across the nutrient poor cryosphere in a warming world. Up-scaling of our observations indicated the potential for glacier algal assemblages to accumulate ∼ 29 kg C km2 and ∼ 1.2 kg N km2 within our marginal surface ice location by the mid-ablation period (early August), confirming previous modeling estimates. While the long-term fate of glacier algal autochthonous production within surface ice remains unconstrained, data presented here provide insight into the possible quality of dissolved organic matter that may be released by assemblages into the surface ice environment.

Algal Toxic Compounds and Their Aeroterrestrial, Airborne and other Extremophilic Producers with Attention to Soil and Plant Contamination: A Review

The review summarizes the available knowledge on toxins and their producers from rather disparate algal assemblages of aeroterrestrial, airborne and other versatile extreme environments (hot springs, deserts, ice, snow, caves, etc.) and on phycotoxins as contaminants of emergent concern in soil and plants. There is a growing body of evidence that algal toxins and their producers occur in all general types of extreme habitats, and cyanobacteria/cyanoprokaryotes dominate in most of them. Altogether, 55 toxigenic algal genera (47 cyanoprokaryotes) were enlisted, and our analysis showed that besides the “standard” toxins, routinely known from different waterbodies (microcystins, nodularins, anatoxins, saxitoxins, cylindrospermopsins, BMAA, etc.), they can produce some specific toxic compounds. Whether the toxic biomolecules are related with the harsh conditions on which algae have to thrive and what is their functional role may be answered by future studies. Therefore, we outline the gaps in knowledge and provide ideas for further research, considering, from one side, the health risk from phycotoxins on the background of the global warming and eutrophication and, from the other side, the current surge of interest which phycotoxins provoke due to their potential as novel compounds in medicine, pharmacy, cosmetics, bioremediation, agriculture and all aspects of biotechnological implications in human life.

The paradox of increasing long-term carbon sequestration in lake ecosystems despite reoligotrophication : the case of four large French perialpine lakes

&lt;p&gt;Although lakes only represent a small fraction of the surface of the earth, a growing number of studies have shown that they play a critical role in the global carbon cycle (&lt;sup&gt;[i],[ii],[iii]&lt;/sup&gt;), mediating carbon transfer from land to the atmosphere, and burying organic carbon in their sediments. The magnitude and temporal variability of carbon burial is, however, poorly constrained, and the degree to which lake productivity has influenced lake carbon cycling has not been systematically assessed (&lt;sup&gt;[iv]&lt;/sup&gt;). Here, trends in total organic carbon (TOC) sequestration and primary production are reconstructed from sediment records for the last 300 years in four perialpine deep lakes. We rely on High Performance Liquid Chromatography (HPLC) and geochemical proxies to investigate changes in algal communities. Then, we evaluate the temporal contribution of algal assemblages to the variability of lake primary production, as well as the potential effects on carbon sequestration magnitude. Other contributors to carbon sequestration derived from the IPER RETRO project (2009-2013) are also investigated, such as past oxygen conditions, lake thermal structure or allochthonous supplies of carbon. Our results suggest that despite reoligotrophication of all lakes (e.g., decrease in dissolved phosphorus concentration in water column and relative restoration of diatoms communities (&lt;sup&gt;[v]&lt;/sup&gt;)) over the last 3 decades, TOC in lakes sediments is still increasing in the sediment. The study of algal pigments suggests that changes in algal assemblages and oxygen conditions could be responsible of this persistent increase in carbon burial. Future development (e.g., DNA analysis) should provide more detail on algal communities to validate these results.&lt;/p&gt;&lt;div&gt;&lt;br&gt;&lt;div&gt; &lt;p&gt;[i] J. J. Cole et al., &amp;#8216;Plumbing the Global Carbon Cycle: Integrating Inland Waters into the Terrestrial Carbon Budget&amp;#8217;, Ecosystems 10, no. 1 (May 2007): 172&amp;#8211;85, https://doi.org/10.1007/s10021-006-9013-8.&lt;/p&gt; &lt;/div&gt; &lt;div&gt; &lt;p&gt;[ii] Tom J. Battin et al., &amp;#8216;Biophysical Controls on Organic Carbon Fluxes in Fluvial Networks&amp;#8217;, Nature Geoscience 1, no. 2 (February 2008): 95&amp;#8211;100, https://doi.org/10.1038/ngeo101.&lt;/p&gt; &lt;/div&gt; &lt;div&gt; &lt;p&gt;[iii] Lars J. Tranvik et al., &amp;#8216;Lakes and Reservoirs as Regulators of Carbon Cycling and Climate&amp;#8217;, Limnology and Oceanography 54, no. 6part2 (November 2009): 2298&amp;#8211;2314, https://doi.org/10.4319/lo.2009.54.6_part_2.2298.&lt;/p&gt; &lt;/div&gt; &lt;div&gt; &lt;p&gt;[iv] N. J. Anderson et al., &amp;#8216;Anthropogenic Alteration of Nutrient Supply Increases the Global Freshwater Carbon Sink&amp;#8217;, Science Advances 6, no. 16 (April 2020): eaaw2145, https://doi.org/10.1126/sciadv.aaw2145.&lt;/p&gt; &lt;/div&gt; &lt;div&gt; &lt;p&gt;[v] Vincent Berthon et al., &amp;#8216;Trophic History of French Sub-Alpine Lakes over the Last 150 Years: Phosphorus Reconstruction and Assessment of Taphonomic Biases&amp;#8217;, Journal of Limnology 72, no. 3 (September 2013): 34, https://doi.org/10.4081/jlimnol.2013.e34.&lt;/p&gt; &lt;/div&gt; &lt;/div&gt;

Species composition, substrate specificity, and seasonal abundance of periphytic algae in a tropical riverine system Periyar, India

The study was conducted to assess the species composition, substrate specificity, and seasonal abundance of periphytic algae from the river Periyar. Monthly samples were collected for one year (June 2016 – May 2017) from different substrates of five selected stations. Eight physicochemical variables such as temperature, dissolved oxygen, pH, conductivity, chloride, sulfate, nitrate, and phosphate were also monitored during the study. Taxonomic studies recorded 156 species of periphytic algae belonging to 56 genera, 36 families, and 5 classes. Naviculaceae was the most abundant family followed by Fragilariaceae and Pinnulariaceae. The principal component analysis revealed the dominance of periphytic algae in the pre-monsoon period. Canonical correspondence analysis indicates pH, conductivity, and sulfate plays a crucial role in periphytic algal assemblages. Correspondence analysis and percentage abundance among different substrates showed the preference of leaf substrate for primary colonization and subsequent succession. The study signifies the importance of substratum and environmental variables in the dynamics of periphytic algal community composition and abundance.