Rachel filters water collected at 500 m in the GOM
Rachel Thomas from Florida State University's Earth Ocean and Atmospheric Sciences Department is a doctoral student in the Knapp Lab and she is our guest-blogger today sharing a bit of her research and cruise goals:
"My personal goal on this cruise is to be able to identify bluefin tuna through a microscope. I’ve never seen fish larvae before, so everything the “fish team” brings up in the nets is new and exciting to me! Most of my previous work is involved in the Southern Ocean, where there are unused nutrients in the surface ocean. This gives us a unique ability to look at how phytoplankton are reacting to different physiological stresses, such as light and nutrient availability."
One of these nutrients, is Nitrate (NO3) which is a form of dissolved inorganic nitrogen that is utilized by phytoplankton in the ocean (Malerba et al 2012). One of the aspects of our project (NF1704 & NF1802 is to examine the dynamics between these inorganic compounds at different depths of the surface water column (0-500 m).
Typical nitrate vertical profile comparison, (modified from A. Nahian Avro)
T. Kelly and Rachel Thomas recover the CTD rosette
"The Gulf of Mexico has a very different light regime compared to the Southern Ocean, and little to no nitrate in the surface waters. Our research team hopes to explore how these contrasts are expressed in the isotopic composition of subsurface nitrate in the Gulf of Mexico. We will also use the isotopic composition of subsurface nitrate in the Gulf of Mexico to understand the nutrient sources for primary productivity fueling bluefin tuna growth in surface waters."
Click here for last year's blog post from Rachel's experiences during NF1704.
A bit of trivia: the Southern Ocean is the fourth largest of the world's ocean basins and extends to Antarctica. Psst, how many oceans are there? (click here for an answer)
Rachel Thomas and Alanna Mnich ready to deploy an SVP drifter on the fan tail
Before we return back to our corresponding labs, and start to process our samples, we have one more post from one of our collaborators! Dr. Bob Arnone was part of the land-support team which guided our survey with satellite updates and oceanographic analyses of daily conditions. The GOM is a very large and dynamic ecosystem and we can use all the help we can get! Bob and two post-doctoral researchers (Brooke Jones and Inia Soto) prepared a blog post to share some of their work at the University of Southern Mississippi. I hope you enjoy it and next year, we encourage our collaborators to do joint posts like this one to share their land based work as well!
Robert Arnone and Brooke Jones in the OWX showing the cruise track
of the Nancy Foster in the Gulf of Mexico and the daily ocean conditions
"We are Prof. Robert Arnone, Dr. Brooke Jones, and Dr. Inia Soto from the University of Southern Mississippi, Division of Marine Science, Stennis Space Center. Our Ocean Weather Laboratory (OWX) was able to work with the researchers aboard the Nancy Foster during the RESTORE Bluefin tuna survey (NF1704) this past May and early June 2017. We provided daily updates on relevant ocean conditions while we followed the ship's cruise track as well as abnormal conditions that might affect the research results. Many of the ocean products we provided are new, and working with the Foster cruise allowed us to compare the observations from our lab with ship observations. Our goal is to demonstrate that our daily ocean products can provide the Foster a better understanding of sampling for Bluefin tuna. We want to continue to work with the research group to optimize our products and the packages we provide.
"The OWX Laboratory was established to characterize the daily ocean conditions and abnormal events in the Gulf of Mexico. Our focus is to assemble products from satellite remote sensing ocean color data, sea surface temperature, and several physical ocean circulation models to define ongoing ocean activity. Our daily products include the ocean bio-optical properties of chlorophyll-a, turbidity, water clarity, phytoplankton absorption, and particle back-scattering and physical oceanographic conditions (temperature, salinity, currents, mixed layer depth). The OWX Laboratory research is focused on the understanding of the interactions between the oceanographic conditions and the ecosystem. New OWX products also include weekly dynamic "anomalies" which can help us identify abnormal physical or biological conditions that are occurring so possible bio-physical oceanographic events can be identified in the Gulf of Mexico.
The Ocean Weather Laboratory at USM with various screens visually monitoring ocean conditions using Google Earth
"The daily OWX Laboratory products provided locations to the Foster for adaptive sampling to help support optimum data collection and understand how Bluefin tuna are responding to changing bio-physical conditions, as well as identify events such as harmful algal blooms, flooding events, coral reef mortality, and others that may be occurring in the Gulf of Mexico.
"The OWX Laboratory visually displays animated ocean properties in several monitors using Google Earth. These tools provide capability to integrate ship tracks and observed data with satellite and model data so we can coordinate with ship operations.
"The videos below show Google Earth animations of the OWX Lab's animated daily products of the nowcast bio-physical processes (Chlorophyll, currents, and salinity) and the dynamic abnormal ocean conditions with the ship track for the Nancy Foster Bluefin tuna survey for the week (May 22-27, 2017)."
We love to share our collaborators' research, especially when the OWX Lab's main focus is to provide new capabilities for ship sampling so that optimum data can be collected and related to the changing ocean conditions. We hope that the daily OWX products can be used for fisheries applications very soon!
And....we're back! Back in the Gulf of Mexico (GoM), on the hunt for larval bluefin tuna (BFT)! The next two legs of our survey will be focused on finding patches of bluefin larvae (Thunnus thynnus), and studying the biogeochemical habitat in which we find them. We are joined by some familiar collaborators from the University of Miami-RSMAS, El Colegio de la Frontera Sur (ECOSUR), and the Spanish Institute of Oceanography (IEO), as well as some new team members!
A glimpse of some of the new equipment we'll be using!
Why is this important? Well, you may know that BFT are one of the mostly highly sought after fish in the commercial industry, as they are large, delicious, and highly valuable. But this also means that they are being over exploited - which means that the levels at which they are currently fished are not sustainable long-term. Atlantic BFT are highly migratory species (HMS), distributed throughout the northern Atlantic Ocean. However, they migrate south to the GoM and the Mediterranean Sea to spawn only once a year during the summer months.
The FORCES lab studies the early life stages of tunas in order to tell their "origin story." Why do the adults travel miles and miles to this specific area? Are there certain oceanic features that provide a protective nursery habitat for the larvae and increase their chances for survival? Are there certain biochemical gradients in these waters that help the larvae grow faster or more fit for surviving the pelagic environment? How will forecasted changes in this environment affect larvae in the coming decades?
LOTS of water filtration will be involved!
We are incredibly excited to be embarking upon a brand new set of surveys with several new partners in order to start to answer some of these questions. We even more thrilled that our new research team was selected as one of the few projects funded by the NOAA RESTORE Act Science Program! This Science Program funds "research, observation, and monitoring to support long-term sustainability in the GoM ecosystem, including fish stocks, fish habitat, and fishing industries" (for more on the program, click here). The FORCES Lab at the NOAA Southeast Fisheries Science Center teamed up with Scripps Institute of Oceanography, Florida State University, and the University of Hawaii at Manoa to examine the "Effects of nitrogen sources and plankton food web dynamics on habitat quality for larval BFT." Together, we will use net tows, satellite data, oceanographic models, and drifters, to find patches of bluefin tuna larvae in the GoM and then we will follow these patches over the next few days. Every day we will sample (around the clock!) the in situ conditions and characteristics of the patch, in order to obtain a bottom-up understanding of BFT recruitment in the GoM. We will share with you more as we keep drifting with the tunas!
We can't wait to share this new journey with you!
Don't worry, we'll still show you loads of sunsets at sea
Where is the best place to catch fish? Alas, a question that
plagues not only the fisherman, but the fisheries oceanographer as well. Ocean
conditions and transport mechanisms play a vital role in the lives of the fish
(and other creatures) that dwell there. Hours after spawning, ocean currents
are sweeping fertilized fish eggs away from their spawning location. If the
temperature is just right, the eggs hatch into larval fish where ocean features
such as eddies will ultimately determine if the fish will find its favorite food
and grow into an adult.
How do we find these ever-changing phenomena so we can study
the effect they have on larval fish? Well...we have some tools.
Satellites
You may find it strange that we use satellites orbiting hundreds
of miles above the Earth to find habitat for larval fish that can only be
examined under a microscope, but it’s true! From the deck of a ship, one patch
of blue water often looks like the next, which is why we call on instruments
such as the Advanced Very High Resolution Radiometer (AVHRR) to do our sensing. A radiometer is a high-tech piece of
equipment mounted on an orbiting satellite that detects radiation which can be used for remotely determining
cloud cover, or, in our case, sea surface temperatures. Our collaborators at
Roffer’s Ocean Fishing Forecasting Services, Inc. (ROFFSTM) analyze the satellite data to provide us with a picture of
where the boundaries between distinct water masses (“fronts”) are. The color image below makes it easy to see the fronts differentiated
by surface temperature.
Satellite image and analysis analysis from ROFFS showing sea surface temperature (SST), currents (blue arrows), completed/planned stations (pink Xs) and future possible sampling locations (red Xs)
We know certain species such as Atlantic bluefin tuna often
spawn near fronts, so this helps us in determining where the best areas to
sample for larvae are. But satellites have their limitations. Despite the
Caribbean’s reputation for sunny beaches, the clouds do occasionally roll in
and prevent the satellites from “seeing” the ocean surface.
Circulation Models
While satellites provide accurate, near-real time
information, sometimes it is useful to get an estimate of what the future
holds. Ocean general circulation models such as the Hybrid Coordinate Ocean
Model (HYCOM) use environmental inputs and complex mathematical formulas
to produce predictions of ocean parameters such as Sea Surface Temperature (SST)
and the speed and direction of ocean currents.
HYCOM model output for sea surface temperature (degrees Celsius)
HYCOM model output for ocean currents (arrows show direction, colors show speed in cm/second)
While the model is not a perfect
predictor, it proves useful on cloudy days or when you want to do some advance
planning which is almost always necessary on a ship that has a maximum speed of
10.5 knots (~12 mph).
Ship Data
Having the support of satellites endlessly gathering data
and computers constantly running models are great assets to what we do…but so
is having access to a high-tech research vessel! Flow through sensors show
real-time sea surface temperature and salinity as the ship is sailing and echo
sounders are pinging the bottom and displaying a precise depth. But perhaps the
most important tool aboard to detect frontal zones is the Acoustic Doppler
Current Profiler, also known as the ADCP.
ADCP output from the 2015 survey across the Yucatan Channel. The ship's track is in black with the direction and size of the arrows showing the direction and speed of the current. Color indicates SST.
The ADCP uses sound waves and the Doppler Effect to measure how fast
water is moving in the water column. What does all this jargon mean? It means
that we can detect the speed and direction of the current directly below the
ship…while the ship is moving! So once we consult the satellite images and
model outputs, the ADCP confirms that we have arrived at the right spot. Then
it is time to tow some nets…
