Collaborative Research: Does larval transport or physiological tolerance set the southern range boundary of a northern blue mussel?

智力价值该项目将测试北方蓝贻贝(Mytilus Trossulus)的南部范围边界是由幼体扩散的限制决定的，还是由幼体和/或幼体的生理耐受性决定的。紫贻贝及其姊妹种紫贻贝在加拿大沿海各省和缅因州北部共同出现。虽然特鲁斯苏拉分枝杆菌的数量在加拿大边境以南突然减少，但蓝枝分枝杆菌向南延伸到北卡罗来纳州。到目前为止的工作已经证明：1)缅因州东北部的成年特鲁斯苏勒分枝杆菌栖息在缅因州东部海岸流(EMCC)较冷的水域内的沿海地点、岛屿和人造建筑物中。2)在EMCC释放的漂流物很少进入南部近岸水域，这表明跨陆架运输极其有限。3)两种幼虫的耐热性可能略有不同，一些证据表明，耐热性也可能受到营养状况的影响。4)在缅因州东北部、EMCC外移栽的紫贻贝存活率较高，向西南方向移栽死亡率较高。综上所述，这些结果表明，幼虫的运输在缅因州东北部(10公里的尺度)内设定了最近的活动范围边界，但热耐受最终将限制更大的空间尺度(200公里)的分布。本研究项目旨在通过野外和实验室实验相结合的方式来验证这一对假设。在幼虫扩散季节(6月中旬至8月中旬)，安装有温度记录仪的卫星漂移器将用于量化幼虫扩散期间的物理流场和温度状况。Drogues将使我们能够评估不同深度的幼虫是否会经历不同的流场。将利用水文调查的数据，结合对贻贝幼虫和新定居者的定期空间和时间采样，评估幼虫和定居后阶段以及不同水团之间可能存在的联系。新定居者的生理耐受性将通过移植到EMCC内外的地点进行测试。最后，实验室的生长和存活实验将分析幼虫在不同温度和饲养方式下的表现。研究人员将使用分子标记来识别这些兄弟物种的形态难以区分的幼虫和定居者。布罗德影响该项目将为一名MS和一名博士生以及几名本科生提供培训。PIs位于强调本科生和研究生研究的机构，我们的项目将为学生提供大量在海洋学和海底生态学领域进行实地和实验室研究的机会。这样的研究机会可能会吸引许多原本会从事生物医学研究的学生。缅因湾是蓬勃发展的紫贻贝水产养殖业的大本营，而紫贻贝是一个商业上较差的物种--种植者担心它可能会蔓延。因此，更好地了解决定该物种范围边界的因素将有助于种植者避免黄曲霉发生口角。将传播结果，以加强与缅因州水产养殖界的沟通。所有的实地工作将在缅因州面临巨大教育挑战的地区进行；将从该地区的学校招聘教师，以协助夏季实地和实验室工作。

Intellectual MeritThis project will test whether the southern range boundary of a northern blue mussel, Mytilus trossulus, is determined by limitations on the dispersal of larvae, or the physiological tolerance of larvae and/or juveniles. Mytilus trossulus and its sister species, M. edulis, co-occur throughout the Canadian maritime provinces and the northern Gulf of Maine. While the abundance of M. trossulus decreases abruptly south of the Canadian border, M. edulis ranges south to North Carolina. Work to date has demonstrated that: 1) Adult M. trossulus in northeastern Maine inhabit coastal sites, islands, and man-made structures that are within the colder water of the Eastern Maine Coastal Current (EMCC). 2) Drifters released in the EMCC rarely enter nearshore waters to the south, suggesting that across-shelf transport is extremely limited. 3) Larvae of the two species may differ slightly in thermal tolerance, and some evidence suggests that tolerance may also be affected by nutritional status. 4) Mytilus trossulus juveniles transplanted within the northeastern Maine region, but outside of the EMCC, have high survivorship, while transplants further to the southwest suffer high mortality. In combination, these results suggest that larval transport sets the proximate range boundary within northeastern Maine (on a scale of 10 km), but thermal tolerance would ultimately limit the distribution on a larger spatial scale (200 km).This research project is designed to test this pair of hypotheses via a combination of field and lab experiments. Satellite drifters equipped with temperature loggers deployed in and out of the EMCC during the season of M. trossulus larval dispersal (mid-June to mid-August) will be used to quantify the physical flow fields and temperature regimes during larval dispersal. Drogues will allow us to assess whether larvae at different depths may experience different flow fields. Data from hydrographic surveys, combined with regular spatial and temporal sampling of mussel larvae and new settlers, will be used to assess possible associations between larval and post-settlement stages and different water masses. The physiological tolerance of new settlers will be assayed via transplants to sites in and out of the EMCC. Finally, laboratory growth and survival experiments will assay larval performance in different thermal and feeding regimes. The investigators will use molecular markers to identify the morphologically indistinguishable larvae and settlers of these sibling species.Broader ImpactsThis project will provide training for one MS and one PhD student, and several undergraduates. The PIs are at institutions that emphasize undergraduate and graduate research, and our project will provide numerous student opportunities for field and laboratory research in oceanography and benthic ecology. Such research opportunities are likely to attract a number of students who would otherwise pursue careers in biomedical research. The Gulf of Maine is home to a thriving Mytilis edulis aquaculture industry, and M. trossulus is a commercially inferior species - growers are concerned about its possible spread. Hence a better understanding of the factors determining the range boundary of this species will help growers avoid M. trossulus spat. Results will be disseminated to enhance communication with the Maine aquaculture community. All of the fieldwork will be conducted in a region of Maine facing great educational challenges; teachers from area schools will be recruited to assist with summer field and laboratory work.