Seasonal sea ice, the cold pool and gadid distribution on the Bering Sea shelf

Thesis (Ph.D.) University of Alaska Fairbanks, 1995The variability in winter seasonal sea ice cover, its impact on the summer hydrography of the Bering Sea shelf, and the consequences to the demersal distributional patterns of walleye pollock (Theragra chalcogramma) and Arctic cod (Boreogadus saida) were investigated. Winter ice conditions acquired by remote sensing techniques were compared to the following summer's hydrographic conditions and fish distributions acquired from fisheries surveys between 1972-1993. Linkages among atmospheric, oceanic, and biological interactions occurred on two scales, an interannual mode of warm or cold conditions and multi-annual regimes of warm, cold or mixed conditions. The southernmost extent of sea ice as measured along meridian 169\sp\circW (P\sb{\rm S}) can be used to identify warm or cold conditions on the shelf. Warm conditions occurred when P\sb{\rm S} extended southward, between 60\sp\circ-57\sp\circ30\sp\primeN, bottom temperatures were 3.8\sp\circ-4.6\sp\circC and the subsurface cold pool of water extended eastward, between meridians 170\sp\circ-166\sp\circW. Cold conditions occurred when P\sb{\rm S} extended southward, between 57\sp\circ30\sp\prime-56\sp\circN, bottom temperatures were 1.2\sp\circ-3.0\sp\circC and the subsurface cold pool of water extended eastward, between meridians 163\sp\circ-158\sp\circW. During the 20 year time series of climatic conditions, three regimes occurred: a cold regime prevailed from 1972-1977, a warm regime from 1978-1984, and a mixed regime from 1985-1991. Age-1 and age-2 and older walleye pollock were primarily in the outer domain during cold conditions and in the middle and inner domain during warmer conditions. Arctic cod were present during cold conditions. Shifts in distribution of these species have ecosystem-wide consequences and can occur on either interannual scales or on the time-scale of regime shifts. Changes in the level of piscivorous predation on age-1 pollock, including cannibalism, occurred on the annual scale while prey species of seabirds and marine mammals fluctuated on the regime scale. Warm or cold summertime conditions were predictable from the previous winter's ice extent, which provides basic information on the level of environmental variability that affects biological systems and can be utilized in modeling this system. The results predict that older pollock will be concentrated in the outer domain following winters with extensive ice, information which could be useful to the fishing industry

Further Evidence for Seed Size Variation in the Genus Zostera: Exploratory Studies with Z. japonica and Z. asiatica

Recent studies found seed size variation within the seagrass Zostera marina, one of nine species in the genus Zostera. The objectives of this study were to determine if variation also exists in the seeds of two other species Zostera japonica and Zostera asiatica within this genus. Results indicate that: (1) length and weight varied between two populations (one indigenous population from Akkeshi-Ko, Japan, and one exotic population from Willapa Bay, Washington, USA) of the small-bodied intertidal seagrass species Z. japonica, and (2) seed-size classes were discernable. Preliminary investigations were also initiated with a Japanese population of Z. asiatica, a large-bodied subtidal seagrass species. Z. japonica seeds from the exotic population were significantly (P \u3c 0.00 1) longer and heavier when compared to those from the indigenous population, a finding which may help explain both the process of the earlier introduction and the recent expansion of this exotic in the northeastern Pacific. Also, preliminary results indicate that Z. asiatica seeds are heavier than both those of Z. marina and Z. japonica, which suggests that larger seeds may be associated with large-bodied plants in this genus, an observation that should direct future seed ecology studies within the genus. These findings demonstrate that, similar to the study of terrestrial angiosperms, investigations designed to describe the comparative ecology of marine seed-bearing plants should include an evaluation of seed size

Restoring damaged and declining eelgrass in the San Juan Archipelago: a pioneering program using seeds

The importance of eelgrass (Zostera marina) comes alive through the Coast Salish people’s cultural stories and practices. The presence of these marine flowering plants is important for culturally iconic species such as the Dungeness Crab and Pacific Herring. In the San Juan Archipelago, loss of historical spawning sites for herring appears to coincide with eelgrass decline. In an effort to offset eelgrass decline, the Puget Sound Eelgrass Recovery Strategy outlines a program that includes a plan to “restore and enhance damaged or declining eelgrass beds”. The uprooting and replanting of adult eelgrass plants is commonly used as a restoration technique. However, throughout the range of eelgrass in the Northern Hemisphere the collection and dispersal of eelgrass seeds has been put forward as a low-cost and effective alternative. This technique is proposed because, after pollination, fertilization, and seed development, eelgrass flowering heads disperse a yearly seed rain, and these seeds populate available habitat either within the bed or a distant location. When seeds settle on the ocean floor in suitable conditions, seedlings sprout, and new patches form. In spring 2020, we launched a pilot program at the Friday Harbor Laboratories, University of Washington, to restore eelgrass in the nearshore region of Bell Point in Westcott/Garrison Bays using seeds. In this poster presentation we illustrate a step wise description of our program that includes methods to: 1) estimate seed to ovule ratios to guide flowering head collection; 2) harvest flowering heads while limiting damage to the donor population; 3) capture the season of peak seed release; 4) efficiently gather and store seeds before planting; and 5) deliver seeds to a restoration site. We will also provide an estimate of human hours, supplies and construction materials needed to replicate our program at other sites in the Salish Sea

Competition between the invasive macrophyte Caulerpa taxifolia and the seagrass Posidonia oceanica: contrasting strategies

<p>Abstract</p> <p>Background</p> <p>Plant defense strategy is usually a result of trade-offs between growth and differentiation (i.e. Optimal Defense Theory – ODT, Growth Differentiation Balance hypothesis – GDB, Plant Apparency Theory – PAT). Interaction between the introduced green alga <it>Caulerpa taxifolia </it>and the endemic seagrass <it>Posidonia oceanica </it>in the Mediterranean Sea offers the opportunity to investigate the plausibility of these theories. We have accordingly investigated defense metabolite content and growth year-round, on the basis of an interaction gradient.</p> <p>Results</p> <p>When in competition with <it>P. oceanica, C. taxifolia </it>exhibits increased frond length and decreased Caulerpenyne – CYN content (major terpene compound). In contrast, the length of <it>P. oceanica </it>leaves decreases when in competition with <it>C. taxifolia</it>. However, the turnover is faster, resulting in a reduction of leaf longevity and an increase on the number of leaves produced per year. The primary production is therefore enhanced by the presence of <it>C. taxifolia</it>. While the overall concentration of phenolic compounds does not decline, there is an increase in some phenolic compounds (including ferulic acid and a methyl 12-acetoxyricinoleate) and the density of tannin cells.</p> <p>Conclusion</p> <p>Interference between these two species determines the reaction of both, confirming that they compete for space and/or resources. <it>C. taxifolia </it>invests in growth rather than in chemical defense, more or less matching the assumptions of the ODT and/or PAT theories. In contrast, <it>P. oceanica </it>apparently invests in defense rather than growth, as predicted by the GDB hypothesis. However, on the basis of closer scrutiny of our results, the possibility that <it>P. oceanica </it>is successful in finding a compromise between more growth and more defense cannot be ruled out.</p

Posidonia oceanica and Zostera marina as Potential Biomarkers of Heavy Metal Contamination in Coastal Systems

International audienc

Managing marine disease emergencies in an era of rapid change

Infectious marine diseases can decimate populations and are increasing among some taxa due to global change and our increasing reliance on marine environments. Marine diseases become emergencies when significant ecological, economic or social impacts occur. We can prepare for and manage these emergencies through improved surveillance, and the development and iterative refinement of approaches to mitigate disease and its impacts. Improving surveillance requires fast, accurate diagnoses, forecasting disease risk and real-time monitoring of disease-promoting environmental conditions. Diversifying impact mitigation involves increasing host resilience to disease, reducing pathogen abundance and managing environmental factors that facilitate disease. Disease surveillance and mitigation can be adaptive if informed by research advances and catalysed by communication among observers, researchers and decision-makers using information-sharing platforms. Recent increases in the awareness of the threats posed by marine diseases may lead to policy frameworks that facilitate the responses and management that marine disease emergencies require

Oysters and Eelgrass: Potential Partners in a High PCO2 Ocean

Ocean acidification (OA) threatens calcifying organisms such as the Pacific oyster, Crassostrea gigas. In contrast, eelgrass, Zostera marina, can benefit from the increase in available carbon for photosynthesis found at a lower seawater pH. Seagrasses can remove dissolved inorganic carbon from OA environments, creating local daytime pH refugia. Pacific oysters may improve the health of eelgrass by filtering out pathogens such as Labyrinthula zosterae, which causes eelgrass wasting disease (EWD). Using a laboratory experiment, we found that co-culture of eelgrass with oysters reduced the severity of EWD. EWD was also reduced in more acidic waters, which negatively affect oyster growth