Showing 1351 - 1360 of 2570 Items
Reflections questionnaire response by Anonymous on April 1, 2021
Date: 2021-01-01
Creator: Anonymous
Access: Open access
- This is a response to the Documenting Bowdoin & COVID-19 Reflections Questionnaire. The questionnaire was created in March 2021 by staff of Bowdoin's George J. Mitchell Department of Special Collections & Archives. The author is from the class of 2022.
Reflections questionnaire response by Anonymous on March 31, 2021
Date: 2021-01-01
Creator: Anonymous
Access: Open access
- This is a response to the Documenting Bowdoin & COVID-19 Reflections Questionnaire. The questionnaire was created in March 2021 by staff of Bowdoin's George J. Mitchell Department of Special Collections & Archives. Author is class of 2024.
Using data from the LISST-100 to recreate phytoplankton size distribution and processes in Harpswell Sound, Maine
Date: 2014-08-01
Creator: Schuyler Nardelli
Access: Open access
- Phytoplankton are the simple single-celled photosynthesizers that live in the ocean and form the base of the food chain. Cell size is a basic proxy for physiological rates as well as ecosystem structure. Thus, cell size can be used in a model framework to track changing environmental conditions that could potentially lead to harmful algal blooms (HABs, aka “red tides”)—events that can be detrimental to human health, marine life, and fisheries. HABs occur when a single algae (phytoplankton) species either grows unconstrained to a concentration such that it becomes toxic or causes low oxygen concentration in the water. In typical estuaries, less dense freshwater flows towards the ocean, and denser salty seawater flows into the estuary in the subsurface. However, Harpswell Sound is a reverse estuary that receives its freshwater input at its mouth from the upstream Kennebec River. This yields upstream surface low salinity flow and downstream deep high salinity flow. This rare dynamic allows phytoplankton located in the surface of seawater to be retained in the sound in conditions conducive to high growth and HABs, and can be used as a warning for conditions throughout the Gulf of Maine. To study the temporal and spatial dynamics of phytoplankton in the sound, we used the LISST-100, which uses light scattering properties to collect continuous in-situ water column observations of particle concentrations and size distributions. Although the LISST-100 was built to measure sediment size with a spherical shape, studies have been conducted that show it can accurately describe a diverse range of phytoplankton shapes and sizes, provided the population has sufficient size differences and is fairly concentrated, conditions found in Harpswell Sound. Weekly profiles of the water column were collected at the Bowdoin Buoy from 5/21/14-6/18/14, as well as a 20-day continuous time series collected at Bowdoin’s Coastal Studies Center dock from 5/30/14-6/18/14 along with supplementary oceanographic data. We determined that semi-diurnal tidal fluctuations are sufficient to move water masses past the buoy and dock with each tide, thereby connecting them. Phytoplankton were found to be in the 3-50 micron size range, with a peak diameter of approximately 7 microns. Additionally, three independent phytoplankton blooms were observed over the course of the 20-day time series as different water masses flowed through the sound. They were sourced in the oceanic water masses found under the freshened surface layer. Over the five-week period the populations gradually surfaced with their water mass as the overlying freshwater dissipated in the absence of rainfall. The LISST-100 served as a useful tool for determining phytoplankton distribution and dynamics within Harpswell Sound, and with further research there is great potential to continue to increase proficiency with the instrument in order to better understand phytoplankton dynamics and harmful algal blooms. Final Report of research funded by the Rusack Coastal Studies Fellowship.
Certain Uncertainties: Chaos and the Human Experience
Date: 1996-01-01
Creator: Justin G. Schuetz
Access: Open access
- Accompanies an exhibition held at the Bowdoin College Museum of Art from April 17 through June 2, 1996. "This brochure is published with funding from the Andrew W. Mellon Foundation."--Colophon
Vulnerability of eelgrass (Zostera marina) to green crab (Carcinus maenas) invasion
Date: 2014-08-01
Creator: Sabine Y Berzins
Access: Open access
- Eelgrass (Zostera marina) is a perennial seagrass that is widely distributed among the shallow subtidal and intertidal Atlantic coastline of the United States and Canada. A highly productive keystone species, eelgrass helps maintain healthy estuarine and ecosystem functions by stabilizing sediments, regulating water flow, absorbing nutrients, and providing critical habitat for animals including commercially important species like soft-shell clams, blue mussels, and migrating waterfowl. Loss of eelgrass beds can therefore result in degraded water quality, shoreline erosion, and reduced fish and wildlife populations. Historically, the Maine coast supported extensive eelgrass beds. However, between 2010 and 2013, eelgrass distribution in Casco Bay declined in area by over 55%. This decline in eelgrass distribution coincides with a regional population explosion of green crabs (Carcinus maenas), an invasive species that physically disturbs eelgrass while foraging for prey. This summer, I collaborated with several Casco Bay Eelgrass Partners including individuals from the Fish and Wildlife Service, Maine Department of Environmental Protection, and the Friends of Casco Bay. Led by U.S. Geological Survey biologist Dr. Hilary Neckles, this project identifies factors that make eelgrass more or less resilient to invasion by green crabs. In June, we established permanent eelgrass survey transects at five locations spanning eastern Casco Bay. Where possible, two transects were established in different types of sediment (fine or coarse/sandy). Most of the eelgrass loss observed over the past decade has been in fine sediments. The question remains; is eelgrass in coarse sediments prone to similar levels of damage? In addition to differences in substrate type, each site also exhibited varying degrees of eelgrass density, shoot height, green crab density and population structure, and other environmental stressors including light availability, temperature, nutrient availability, and natural physical disturbance. I made biweekly measurements of green crab densities at one site, Widgeon Cove in Harpswell. Crap trapping indicated few green crabs occurred near the Widgeon Cove transect, but traps at the other four Casco Bay sites collected as many as 300 crabs within a 24-hour period. Final measurements in the eelgrass transects will be taken in September and data collection will be completed in October. Data gathered this summer will provide information to help move forward with a plan to protect and potentially restore eelgrass in Casco Bay. Additionally, I identified patches of eelgrass in the Kennebec Estuary that might be viable sites for replanting next summer. I hope to continue working on this project next year, thinking about ways to restore eelgrass to the system while identifying ways to increase trapping pressure on green crabs such that their numbers might be reduced. Final Report of research funded by the Rusack Coastal Studies fellowship.