Currently, 61 transects are monitored by local agencies participating in the TBISP. Data is entered using an
online form and database. Findings of the Tampa Bay transect program are summarized in technical publications (See Avery and Johansson 2001; 2003; 2005; 2006; 2008; and 2010; Johannsson 2016; and Sherwood et al. 2017) and shown in an interactive dashboard. Assessments conducted during the transect surveys include: (1) measurement of seagrass canopy height, evaluation of seagrass condition, short shoot densities (SSD) and percent coverage for all seagrass species present; (2) characterization of epiphytes observed on seagrass blades; (3) measurement of water depth where seagrass is present; (4) sediment type; and (5) density of all macroalgae species present. Transect data, associated metadata, and a description of how to reproduce TBEP analyses and graphics are also available online.
A hands-on field training class is conducted with participating partners in summer prior to the start of the annual transect survey period. The training aims to review sampling procedures and calibrate surveyors by having all partners assess the same training transect.
Instructional videos for the transect monitoring are also available online.
Shortly after the training, comparisons of team surveys are made available on this
dashboard. The dashboard provides a simple summary of precision between sampling teams and, if necessary, supports additional training needs to ensure consistency in data collection. Trends
During more than twenty years of seagrass transect monitoring, the
frequency of occurrence (or the percentage of times that a species appears along a transect during a given year) for both Halodule wrightii (Shoal grass) and Syringodium filiforme (Manatee grass) in Tampa Bay has increased ( Johansson 2016, Sherwood et al. 2017), while the frequency of occurrence for locations where no seagrass was observed has decreased.
A summary graphic for Frequency of Occurrence over time (how often seagrass shows up at a transect during a given year). Values range from 0% (no seagrass, lighter colors) to 100% (complete coverage, darker more blue colors). Numbers in the cells show the actual percent value.
Bay segment changes over time in frequency of occurrence (how often seagrass shows up at a transect during a given year)
Historical seagrass coverage estimates (ca. 1950 and 1982) for Tampa Bay were obtained through photo-interpretation of aerial images (TBRPC 1986; Haddad 1989; Tomasko et al. 2005). In 1988, the SWFWMD began a biennial seagrass mapping program to assess seagrass coverage and monitor seagrass recovery in Tampa Bay. Prior to 2002, aerial photographs were digitized before mapping (Tomasko et al. 2005). More recent assessments (2004–2020) use digitally acquired aerial imagery. Seagrass coverage estimates are based on images acquired during the late fall or early winter and are classified into two categories: patchy or continuous seagrass coverage (
Sherwood et al. 2017). SWFWMD seagrass data are available online. Trends
Numerous public and private sector partners have made significant investments to improve water quality in Tampa Bay. As a result, seagrass coverage has steadily increased since the 1980s. Coverage estimates from the three most recent surveys (2014, 2016, 2018) demonstrate that Tampa Bay harbors more than 40,000 acres of seagrass, a goal identified in the
Habitat Master Plan (2020 Update). Results from the 2020 aerial assessment are anticipated in spring 2021.
Seagrasses have significantly recovered since the 1980s, essentially rebounding to coverage of the 1950s due to improvements in water quality in Tampa Bay.
In 2016, seagrass coverage exceeded levels recorded prior to widespread urbanization within the Tampa Bay watershed. Many locations within the bay proper that contained seagrass in the 1950s also had observable coverage in 2016. The exceptions are primarily in bay segments where historic dredge and fill activities occurred.
SFWFMWD has online seagrass data from 1990-2018 as well as an interactive
Seagrass Story Map.
Five species of seagrass regularly occur in Tampa Bay:
Shoal grass (
Halodule wrightii) is the most common species in the Tampa Bay region. It has narrow, thin, and flat leaves that can grow to about 30 cm (or 1 foot). The leaves grow from short shoots, or seagrass stems, attached to the rhizome, or underground stem. Intact leaves have notched tips similar to a king's crown. This helps differentiate shoal grass and widgeon grass.
Turtle grass (
Thalassia testudinum) is dominant in more salty areas like Lower Tampa Bay, but can also be found in Old Tampa Bay and Middle Tampa Bay. It has flat, wide, ribbon-like leaves, and can grow to a length of more than 50 cm (nearly 2 feet). Turtle grass produces quarter-sized flowers which are often observed in April-May.
Manatee grass (
Syringodium filiforme) is found in all subregions except Hillsborough Bay. It has cylindrical leaves that can grow over 60 centimeters in length (about 2 feet).
Widgeon grass (
Ruppia maritima) is less abundant in Tampa Bay and occurs in more freshwater areas. Widgeon grass looks similar to Halodule, except that the leaves are alternate, and grow from branching points along the main stem. When flowering, very long and leggy branching is present. Pointed tips on the leaves also help to distinguish this species from Halodule.
Photo source: iNaturalist/jiayizhou-zoe
Star grass (
Halophila engelmannii) is also rarely seen in Tampa Bay but is fairly easy to identify. As the name suggests, a group of up to eight short leaves grow from a central base. The leaves are generally less than 3 cm (about 1 inch) long.
Caulerpa sp., Old Tampa Bay
There are also several types of attached and drift algae (large algae that can be seen with the naked eye) that regularly occur in the seagrass beds, such as
Caulerpa, a highly variable drift algae, and Ulva, or sea lettuce.
Photo by Joe Whalen
Some people use pasta to help differentiate a few of the seagrass species common in Tampa Bay: Shoal grass is fine like angel hair, Manatee grass is round like bucatini or spaghetti, and Turtle grass is wide and flat like fettuccine or pappardelle.