How do we sample harbor habitats?

The 2018 Biological Survey of the Ports of Los Angeles and Long Beach was the result of collaboration among over 40 multidisciplinary scientific professionals using a variety of sampling techniques and tools to study the San Pedro Bay.    

So how do scientists study the marine habitats and animals that live here?

Many ways:

• Divers go into the water to perform up-close visual surveys and collect samples. 
• Scientists on boats use nets, bottom grabs, and sensors.
• Aircraft and satellites perform remote sensing of the marine environment.

 Background image: A diver enters the water in the Port of Long Beach.

One of the most reliable methods for collecting data is to send experienced scientific divers into the water to perform visual surveys. Recording the number of animals within a search area gives these researchers information about diversity, density, and the percent of the habitat used by different types of animals. Equipment such as cameras, transect lines, and quadrats are useful to document what is seen, and divers also use special synthetic paper and pencils to record their data underwater!

Background video: Diver counting kelp stipes in the outer harbor.

For animals that are too small or difficult to identify in the field, such as the hundreds of small animals and species of algae that grow on riprap and pilings, sometimes divers must also collect physical samples by hand. These samples are preserved and taken back to the lab for careful identification by taxonomists.

When scientists can’t get into the water, often nets are used to bring animals to the surface in order to study them. Large nets that target animals on the seafloor (trawls) and in the water column (lampara nets) can be deployed from boats, while smaller nets to sample shallow habitats can be used from the shore. Measuring, counting, and weighing the animals gives scientists important information about diversity, abundance, and population details such as the percentage of juveniles in nursery habitats.

Background video: Recovering a lampara net. 

1. A beach seine at Cabrillo Beach. 
2. A plankton net on deck.  
3. An otter trawl in the Main Channel of the Port of Los Angeles.  

To learn more about the physical environment that the animals live in, scientists use different types of grab samplers to capture sediment from the seafloor and water samples at targeted depths. The properties of the sediment (such as how sandy or muddy it is) and the water (salinity, nutrients, etc.) can affect what animals are able to survive in that area. In order to study the animals that can burrow into the seafloor like clams and worms, the sediments are sieved on deck and the animals are taken back to the lab to be studied under a microscope.

Background image: Recovering mud from a Van Veen grab to sieve for animals.

Sensors above and below the water can provide scientists with information that helps them understand the environmental conditions that marine communities are exposed to. Types of sensors include those that can be deployed by hand from boats to measure variables like temperature and water clarity, and buoys maintained by research institutions to monitor oceanographic parameters like tidal height, wave height, and wave direction.

Background image: An oceanographic research buoy (photo courtesy of CDIP).

In order to “see” the seafloor, side-scan sonar uses soundwaves to map the seafloor from a boat on the surface. The reflectance of soundwaves off of features on the seafloor, such as eelgrass beds, shows up as an image on a screen back at the surface. The creation of these images is similar to how doctors use an ultrasound to ‘see’ babies growing and organs inside of a patient. The images of eelgrass can be turned into maps that have helped track the expansion of valuable eelgrass habitat within the Port Complex over the past two decades.

Background image: Snails on eelgrass blades in the outer harbor.

Scientists also rely on sensors in airplanes and satellites to measure characteristics of the ocean surface from up in the sky or all the way out in space using sensors that rely on various non-visible light wavelengths. Referred to as ‘remote sensing’, these methods can provide information such as water temperature, the concentration of planktonic algae, and turbidity (or water clarity), and can even be used to map kelp canopy floating at or below the surface. The information from remote sensing can then be color coded and placed on a map for easy interpretation.

Background image: Landsat 8 Observation Satellite (Image courtesy of NASA’s Goddard Space Flight Center).

Once data from the field sampling are carefully recorded and checked for accuracy, scientists can analyze them to learn more about the biological communities found throughout the harbor. Data are organized into tables and then visualized in a number of ways, from simple graphs showing which sampling stations had the most species to more complex statistical analyses that can show differences in the composition of the biological community in different locations.

Background image: A queenfish being measured on deck.

Over the more than 20 years that the ports have collaborated to monitor biological communities in their harbors, the program continues to evolve to be consistent with other regional monitoring programs and to incorporate new methods. The emergence of new technologies, such as remote sensing and molecular techniques to measure diversity, provides opportunities to improve the quality of data that are collected. Equally important, it affords new insights into how marine communities in the Port Complex have adapted to larger regional trends such as increasing sea surface temperatures and the introduction of non-native species.

Background image: Survey team in front of USS Iowa.