6.7.24

Seagrass survival in a super salty lagoon

A researcher in the Dunton Lab measures seagrasses underwater using a mask, snorkel, and a white PVC quadrat.

The activities are as follows:

Seagrasses are a group of plants that can live completely submerged underwater. They grow in the salty waters along coastal areas. Seagrasses are important because they provide a lot of benefits for other species. Like land plants, seagrasses use sunlight and carbon dioxide to grow and produce oxygen in a process called photosynthesis. The oxygen is then used by other organisms, such as animals, for respiration. Other organisms use seagrasses for food and habitat. Seagrass roots hold sediments in place, creating a more stable ocean bottom. In addition, the presence of seagrasses in coastal areas slows down waves and absorbs some of the energy, protecting shorelines.

Unfortunately, seagrasses are disappearing worldwide. Some reasons include damage from boats, disease, environmental changes, and storms. Seagrasses are sensitive to changes in their environment because they have particular conditions that they prefer. Temperature and light levels control how fast the plants can grow while salinity levels can limit their growth. Therefore, it is important to understand how these conditions are changing so that we can predict how seagrass communities might change as well.

Ken is a plant ecologist who has been monitoring seagrasses in southern Texas for over 30 years! Because of his long-term monitoring of the seagrasses in this area, Ken noticed that some seagrass species seemed to be in decline. Kyle started working with Ken during graduate school and wanted to understand more about what environmental conditions might have caused these changes. 

Manatee grass (Syringodium filiforme) located within the Upper Laguna Madre.

Texas has more seagrasses than almost any other state, and most of these plants are found in a place called Laguna Madre. During his yearly seagrass monitoring, Ken noticed that from 2012 – 2014 one of the common seagrasses, called manatee grass, died at many locations across Laguna Madre. Since then, the seagrass has grown back in some places, but not others. Kyle thought this would be an opportunity to look back at the long-term dataset that Ken has been collecting to see if there are any trends in environmental conditions in years with seagrass declines.

Each year, Ken, Kyle, and other scientists follow the same research protocols to collect data to monitor Laguna Madre meadows. Seagrass sampling takes place 2 – 4 times a year, even in winter! To find the manatee grass density, scientists dig out a 78.5 cm2 circular section (10 cm diameter) of the seagrass bed while snorkeling. They then bring samples back to the lab and count the number of seagrasses. While they are in the field, they also measure environmental conditions, like water temperature and salinity. A sensor is left in the meadow that continuously measures the amount of light that reaches the depth of the seagrass.

Kyle used data from this long-term monitoring to investigate his question about how environmental conditions may have impacted manatee grass. For each variable, he calculated the average across the sampling dates to obtain one value for that year. He wanted to compare manatee grass density with salinity, water temperature, and light levels that reach manatee grass. He thought there could be trends in environmental conditions in the years that manatee grass had low or high densities.

Featured scientists: Kyle Capistrant-Fossa (he/him) & Ken Dunton (he/him) from the U-Texas at Austin

Flesch–Kincaid Reading Grade Level 9.8

Additional teacher resources related to this Data Nugget:

There is another Data Nugget that looks at these seagrass meadows! Follow Megan and Kevin as they look at how photosynthesis can be monitored through the sound of bubbles and the acoustic data they produce.

Follow this link for more information on the Texas Seagrass Monitoring Program, including additional datasets to examine with students.

There are articles in peer-reviewed scientific journals related to this research, including:

National Park Service information about the Gulf Coast Inventory and Monitoring.

Texas Parks and Wildlife information on seagrass:

7.19.21

Buried seeds, buried treasure

Marjorie (right) and David (left) digging up the seed bottle in 2021. This bottle was scheduled to be dug up in 2020, but the experiment was delayed one year due to COVID-19.

One of the world’s longest-running science experiments lies hidden in the soil beneath Michigan State University’s campus. Over 100 years ago, a scientist named William J. Beal had a question: how long do seeds survive underground? To find out, he started an experiment. In 1879 he filled 20 bottles with sand and seeds from local plants. William buried these bottles and created a map to document their location, hoping that future scientists would continue to dig them up to test whether the seeds would still grow long after his death.

These bottles and the map have been passed down from generation to generation, with each new scientist responsible for training their successor. To protect the seeds, only a select few scientists are let in on the secret. Today a team of four plant biologists hold the map, and they were the ones to dig up the most recent bottle in 2021. 

Early one Thursday morning, before the sun had risen, the team set out on their mission. Marjorie Weber, the first woman to be in charge of the study and currently the youngest team member, was the scientist who found the bottle and pulled it from the ground. This is a big deal, as back when William began the experiment women weren’t even allowed to be scientists!

Seeds of Verbascum blattaria germinating in 2021. This is the only species that germinated from the most recent collection.

Originally, the Beal Seed Experiment was designed to test seed viability, or how long seeds of different species stay alive in the soil and still germinate. Seeds don’t germinate as soon as they fall off their mother plant. They become part of a seed bank below the soil, waiting for the right conditions to tell them to sprout. William was working with local farmers in Michigan, and he was interested in helping them better understand how long weeds will continue to pop up in their fields after they start to plant crops. This is reflected in the fact that many of the species included in the experiment are weeds in agricultural fields. 

Despite all the changes that have taken place in the world since the seeds were buried 142 years ago, the main question remains the same: how long can seeds stay alive in the soil? In addition to helping farmers, Marjorie and the other scientists now have additional reasons for wanting to understand seed viability. Restoration of natural plant communities, conservation of endangered species, and removal of invasive plants from fragile ecosystems can all benefit from a knowledge of the seedbank. 

With this long-term study design, scientists can compare how many seeds sprout and which species are able to germinate through time. Originally, William dug up a new bottle every five years. Once scientists realized how long the seeds last, they made the interval between excavations longer; now they wait 20 years before digging up the next bottle. The experiment is set to go at least another 80 years. Imagine, future bottles will be dug up by scientists who are not even born yet!

Once a bottle is found and unearthed, it is taken back to the lab to see which species will germinate. Filled with sand and over a thousand seeds, each bottle contains the same mix of 50 seeds of 21 different species of plants. The contents are spread out on a tray filled with soil and are put into growth chambers. Scientists keep an eye on the trays to watch and see what germinates.

Featured scientist: Marjorie Weber from Michigan State University. 

Other scientists: Frank Telewski, David Lowry, Lars Brudvig, and Margaret Fleming.

Written by: Elizabeth Schultheis and Melissa Kjelvik.

Flesch–Kincaid Reading Grade Level = 9.7

Additional teacher resource related to this Data Nugget:

This experiment received a lot of press coverage. Have students check out these new stories and videos to learn more about the scientists and experiment:

YouTube video summarizing the search and the experiment: