Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • BCO-DMO Processing Description
• Parameters
• Instruments
• Project Information
• Funding

Additional description: These data were collected in the Damariscotta River estuary in Walpole, Maine. Environmental parameters were measured using a YSI-EXO multi-parameter sonde. Environmental measurements were collected approximately 0.5 m above the substrate and therefore, represent bottom-water measurements. Zooplankton were collected from midwater using an 80 micrometer mesh net. Mysid shrimp were collected just above the substrate with a 1000 micrometer mesh net. 

Mysid shrimp and zooplankton collection

Neomysis americana (LSID, urn:lsid:marinespecies.org:taxname:157807) were collected in the Damariscotta River Estuary every 2 weeks from June 2023 and ending in October 2023, giving approximately 12 sample dates for their growing season. Additionally, we conducted high-frequency sampling over three days in August 2023 alongside the optical equipment, giving a total of 20 sampling dates with 2-3 replicates for each sample.  Starting in November 2023, we began sampling monthly and will continue this monthly survey until May of 2024 to capture seasonal patterns. During each sampling trip, we collected samples from the muddy bottom near the pedestrian dock at the Darling Marine Center dock, at a depth of 1.5 - 4 m, depending on the tidal cycle. A 45 cm x 25 cm rectangular 1000 μm net equipped with a flowmeter was deployed from the dock down to the substrate and hand towed along the bottom. The contents of the cod end were emptied into a container on the dock and all mysids were immediately preserved in 4% neutral buffered formalin for later analysis. The same net was then deployed vertically, resting just off the bottom for 2 minutes, to capture mysids in the water column.

To capture smaller zooplankton that might serve as prey for mysids, we lowered an 80 μm mesh ring net with a 0.5 m diameter opening into the water at mid-depth from the dock and let water flow through the for 10 minutes. An attached flow meter was used to estimate the volume of water sampled by the net. Zooplankton were immediately preserved in 15% EtOH and taken to the lab for drying and identification. After splitting the sample with a plankton wheel (Wildco), one half was filtered through a pre-weighed, cone coffee filter and dried in an oven at a temperature of 60°C for 24-48 hours, or until constant weight was achieved. Zooplankton biomass is expressed as mg/m³ according to the formula B = W / V, where B is the zooplankton biomass (mg), W is the weight of the sample, and V is the filtered water volume (m³). The other half of the sample was cold preserved at 4°C in 50% EtOH/seawater until visual analysis, when the organisms were identified to the genus level. Subsample aliquots of organisms 100 individuals were measured to the nearest μm using a dissecting microscope with an attached camera and measuring software (CellSense, Olympus). 

Phytoplankton collection and processing  

To capture phytoplankton that might serve as food for mysid shrimp, we towed a 20 μm plankton net just below the surface along the end of the dock 10 times (approx. 20m). On deck, we rinsed the net with 1L of seawater, washing the sample into a bucket. We then collected a 125ml subsample and preserved with 10ml Lugol’s iodine solution in a dark bottle and stored at 4°C for further analysis. To determine which phytoplankton species were present, a subsample was identified to genus level using a compound microscope.

Environmental parameters

  We conducted vertical profiles of environmental variables using a YSI-EXO multi parameter sonde. Dock samples were collected from the dock at the Darling Marine Center and all other estuarine samples were collected from the R/V Ira C.  To begin a profile, the sonde was lowered by hand at a rate of app. 0.3 ms-1 until the sonde reached the bottom and then slowly raised to the surface. The sonde recorded temperature, salinity, turbidity, and fluorescence throughout the water column. What is reported here in this file are the bottom-water values because these values are most relevant to our target species, Neomysis americana which resides just above the substrate. A related dataset will be provided to BCO-DMO for the entire water column (file processing in progress). 

* Sheet 1 of submitted file "Mysid & Zoop Survey Data RUI 2023_BCO DMO.xlsx" was imported into the BCO-DMO data system for this dataset.
* One date was displayed with format 7/2023 in Excel with underlying value 7/20/2023. The date in the table imported to BCO-DMO uses the underlying full date value to match the other full date formats provided in the table. 7/20/2023 was verified as the correct date by the data submitter.
** Missing data values are displayed differently based on the file format you download.  They are blank in csv files, "NaN" in MatLab files, etc.

* Column names adjusted to conform to BCO-DMO naming conventions designed to support broad re-use by a variety of research tools and scripting languages. [Only numbers, letters, and underscores.  Can not start with a number]

* Date converted to ISO 8601 format
* ISO_DateTime_UTC column added (From local EST/EDT date and times provided)

NSF Award Abstract:
Mysid shrimp are a group of zooplankton that are distributed in diverse aquatic environments – freshwater, marine and estuarine – in both shallow and deep waters throughout the world. Due to their ubiquitous presence, mysids form a critical link in marine food webs, yet little is known about their ecology and interactions with their local surroundings. An interdisciplinary team of investigators will develop and deploy a novel in situ imaging system in coastal Maine over the span of two summers, conducting a comprehensive investigation of mysid behavior in their natural environment, including their interactions and distribution under varying local flow, food, and light conditions. The investigators will train two graduate students at the interface of fluid mechanics, instrumentation, and ecology. In addition, ten students from Florida Atlantic University and the University of Southern Maine will be invited to participate in annual workshops on ecological fluid mechanics, with first-generation college students or those from other underrepresented communities encouraged to apply. The cutting-edge instrumentation suite, including the imaging system being developed as part of this project, can be used to address different questions associated with spatial patterns and zooplankton or fish behavior in the future. Image datasets will be openly accessible to the scientific community and the public. Project results will be disseminated through public outreach lectures at the Harbor Branch Oceanographic Institute, Darling Marine Center, and the Woods Hole Oceanographic Institution.

Mysids have been historically understudied compared to other zooplankton groups (e.g., copepods, krill), despite their ubiquitous presence and importance to marine food webs. This project will investigate mysid behavior, feeding ecology, and swarm distributions in relation to prey availability, light levels, and background flow conditions, focusing on a single mysid species – Neomysis americana. The investigators will use a state-of-the-art suite of instruments in the field, including two separate imaging systems and a high resolution Acoustic Doppler Profiler, to conduct field experiments at the Damariscotta River Estuary. This instrumentation suite will collect data to analyze mysid distributions and animal-fluid interactions in their natural environment, as well as ancillary data on benthic particle/plankton community composition and physical parameters (including currents, waves, temperature and depth). Multi-spectral analysis will find correlation patterns with water turbidity, flow conditions, bottom topography, mysid abundance, and food source concentrations. Mysid samples will be collected several times a week throughout the summer months to monitor changes in the mysid population abundance, sex ratio, and stage structure. The investigators will determine how seasonal changes in environmental variables and Neomysis population structure affect distribution within the estuary, as well as small-scale swimming and aggregation behavior. They will answer questions related to how swarm organization, aggregation, and swimming behavior differ under conditions of varying zooplankton abundance and swarm composition. Results will ultimately improve our understanding of marine ecosystem dynamics.

This project is jointly funded by the Biological Oceanography Program and the Established Program to Stimulate Competitive Research (EPSCoR).

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.