What: Human activities have enhanced nutrient delivery to coastal ecosystems in the northern Gulf of Mexico which has led to extensive eutrophication. By comparing populations living in the region today with the remains of historical populations preserved in marine sediments, we can determine the impacts of anthropogenic eutrophication on marine communities. Between mid-June and mid-July, students will collect live-dead samples offshore Alabama and Louisiana and engage in lab work at Franklin and Marshall College. Student research projects will focus on live-dead and taphonomic comparisons of marine mollusks along a nutrient gradient extending from the Mississippi River east to the nutrient-poor west Florida shelf. These projects will help to establish historical baselines for the diversity, abundance, and ecology of mollusks in subtidal habitats prior to the onset of industrial agriculture and commercial fishing.


Fig 1 Offshore Dauphin Island, Alabama

Fig 1 Offshore Dauphin Island, Alabama

When: June 13 – July 8, 2016 (tentative)

Where: One week in Alabama and Louisiana and three weeks at Franklin and Marshall College in Pennsylvania

Who: Paul Harnik (Franklin and Marshall College) and three students

Project Overview: The Mississippi River watershed drains 40% of the continental United States and is home to approximately 70 million people. The river’s delivery of nutrients has supported tremendous primary production in the marine ecosystems of the northern Gulf of Mexico for millennia; evident today by the network of offshore oil and gas wells that mine the region’s hydrocarbon-rich sedimentary deposits. Human activities have enhanced nutrient delivery to coastal ecosystems in the northern Gulf through farming, urbanization, and surface run-off and, as on land, these additions of nitrogen and phosphorous have spurred primary production. Phytoplankton blooms in the northern Gulf have led to the growth of one of the largest oxygen-limited zones in the world. How has anthropogenic eutrophication affected the marine species that live in the northern Gulf of Mexico?

Answering this question requires a historical perspective, yet long-term biodiversity surveys in the oceans are rare. Live-dead analysis – the comparison of living populations with historical populations represented by dead remains – has emerged as a valuable tool for evaluating historical changes in marine ecosystems that began before the onset of scientific monitoring. Participants in this Keck project will engage in field- and lab-based live-dead studies in the Gulf of Mexico. During summer 2016, we will head offshore Cocodrie, Louisiana and Dauphin Island, Alabama to sample the shells of live and dead marine mollusks from sediments on the continental shelf. These samples, along with collections from Alabama and Florida, will span a nutrient gradient extending from the nutrient-rich Mississippi delta east to the nutrient-poor west Florida shelf. In the lab at Franklin and Marshall College, we will use paleontological methods to gather historical data on the abundance, diversity, and ecology of mollusks preserved in subfossil death assemblages. These baseline data will then be compared with data collected from present-day populations at these same sites. The northern Gulf of Mexico has played a central role in the growing awareness of current threats to marine biodiversity and these projects have the potential to offer critical perspectives on the impacts of human activities on coastal ecosystems.

Potential Student Projects:  All students will participate in the collection and processing of live-dead samples in the field and lab. These samples, and those collected previously by the project director, will be analyzed by students during the 2016-17 academic year. Student research projects will be refined over the summer based on individual interests and based on what is recovered from our new field samples.

Fig 2 Students processing live-dead samples in the northern Gulf of Mexico

Fig 2 Students processing live-dead samples in the northern Gulf of Mexico

  1. Live-Dead analysis of larval shell size

Student(s) will assess variation in larval shell size in different species of mollusks using scanning electron microscopy to test the hypothesis that larval shells today are smaller than those of historical populations. Larval shell size is positively correlated with egg size and life history theory predicts that under high nutrient conditions individuals that produce more numerous, smaller eggs will leave behind more offspring.

  1. Live-Dead analysis of body size

Student(s) will gather body size data to test the hypothesis that live populations consist of smaller individuals on average than historical populations in regions affected by low oxygen, high nutrient (hypoxic) conditions. Student(s) will also have the opportunity to develop educational materials for high school Earth science and biology classrooms that guide high school classes through the process of collecting and analyzing body size data for Gulf mollusks.

  1. Live-Dead agreement in community composition and species abundance

Student(s) will collect and compare molluscan diversity and abundance data to test the hypothesis that live-dead differences are greatest in regions affected by anthropogenic eutrophication.

  1. Taphonomic grade of molluscan death assemblages

Student(s) will collect data on the condition of dead specimens to test the hypothesis that preservational quality declines along a clastic-to-carbonate gradient as has been observed previously in other regions.

Logistics: The project will begin and conclude in Lancaster, Pennsylvania at Franklin and Marshall College. The first week will be spent in the lab preparing for fieldwork and collecting data from existing live-dead samples. Week 2 and the start of week 3 will be spent in Alabama and Louisiana collecting new samples aboard research vessels chartered from two marine labs. Offshore fieldwork will involve long days (8 to 12 hours) on the water. Samples will be collected throughout the day using a sediment grab sampler and/or a box corer. These pieces of equipment are provided by each marine lab and will be deployed by research technicians from the marine lab. Students will be involved in documenting sediment samples, wet-sieving sediments, and sorting specimens of live and dead mollusks > 2mm for later study. We will rotate through these activities throughout the day to ensure that everyone has the opportunity to develop their skills and also to minimize motion sickness (which can be an issue when sorting small specimens on a rocking boat). We will sleep onshore each night. The remainder of week 3 and all of week 4 will be spent at Franklin and Marshall College processing live-dead samples, developing data collection protocols, collecting and sharing preliminary data, and developing independent research projects which will be continued through the 2016-17 academic year.

Field conditions: Offshore fieldwork is tremendously exciting and also quite challenging. Ocean conditions are unpredictable and transit times from the harbor to offshore sampling stations may be lengthy which necessitates long field days as well as flexible and positive attitudes among all project participants. Provided sea conditions are conducive, initial processing of all live-dead samples will occur offshore to ensure adequate sample sizes of live and dead specimens are achieved. Individuals that are prone to motion sickness will likely find these fieldwork conditions challenging. All participants are strongly encouraged to take non-drowsy anti-motion sickness medicine on the days spent offshore to minimize their own discomfort which can impact their experiences and research by the group. Prior boating experience is a plus but is not a requirement. Summer conditions in the Gulf are hot and humid and everyone will need to dress appropriately to minimize sun burn (lots of sun block and a sun hat!) and need to stay hydrated. The research vessels that we will use are outfitted with safety equipment in case of emergency and participants will receive safety instructions by the vessel crew prior to leaving the shore. Cell phone service is generally unavailable offshore however ships are equipped with communication devices in case of emergency.

Recommended Courses/Prerequisites: Participants should have taken a course in paleontology and/or historical geology. Recommended, but not required courses, include marine science, sedimentology and stratigraphy, introduction to ecology and evolution, and statistics.

Contact Information: Paul Harnik, [email protected], 717-358-5946