This study examined the ingestion of microplastics by grunt fish along the Texas Gulf Coast. A total of 122 grunt were collected from four locations and examined. The key findings were: - 29% of grunt contained microplastics in their stomachs, with the highest rates at locations near the mouth of the Brazos River. - Ingested microplastics were primarily blue threads. - The presence of microplastics in grunt was not correlated with fish size. - The study confirms microplastic ingestion by coastal fish and suggests sources may include runoff from the Brazos River.

1. Microplastic Ingestion in Grunt (Orthopristis chrysoptera) Along the Texas Gulf Coast
Savannah Tarpey, Jessica Purtell, Colleen Peters, and Susan P. Bratton
Department of Environmental Science, Baylor University, Waco, TX 76798
ABSTRACT
Plastic microparticles, ranging between 50 and 5000 µm,
reside within marine, freshwater, and deep ocean
environments. While substantial literature has quantified the
ingestion of macroplastics by marine vertebrates, relatively
few studies have focused on the ingestion of microplastics
and artificial polymers, such as polyester and nylon threads.
This study documents microplastic ingestion by grunt
(Orthopristis chrysoptera) from the inshore coastal waters,
between Galveston and Freeport, Texas. A total of 122 grunt
were collected from four sample locations, averaging 17.31
cm in length and 77.94 g in weight. Of the 122 grunt
collected, 35 (29%) stomachs contained ingested
microplastics. Neither fish length (p=0.586, cc=0.050) nor
weight (p=0.899, cc=-0.012) was correlated to microplastic
ingestion. Fish collected from Surfside Jetty had the highest
frequency of microplastic ingestion (61%) and mean number
of particles per fish (1.65), followed by Freeport Channel
(24% and 1.33), 91st Street (20% and 1.25) and San Luis Pass
(14% and 1.00). A total of 50 microplastic items were
collected from grunt stomachs and 98% were in the form of
threads, with blue the predominantly collected color (46.8%).
Additionally, there was one microplastic bead recovered
from a grunt collected from Freeport Channel. There were
no macroplastic items or additional microplastic forms
collected from sample stomachs. While this study confirms
the ingestion of microplastics by grunt, it is probable that
species, feeding method, location, and levels of local
anthropogenic disturbance influence the frequency of
microplastic ingestion.
METHODS
Field collection – Grunt
Between May and August 2015, using hook and line,
sampling teams collected 122 grunt, from 4 sample locations
ranging from Galveston to Freeport, Texas. Sites included
central Galveston around 91st Street, the open ocean side of
Surfside Jetty, San Luis Pass, and the Freeport Jetty.
Collections were taken directly from the beach, jetty, or dock.
Laboratory analysis
Microplastics, including artificial polymers, are defined as 50
to 5000 µm in length. Teams separated stomach contents via
a multi-stage process, by utilizing distilled deionized water to
wash stomach material through four filters; 1000µm, 243µm,
118µm, and 53µm; thereby separating individual food items
into separate size categories. Teams then examined the
stomach content on each filter utilizing a stereo-microscope
using 20 x oculars, and separated items into categories via
taxon (genus or family), anthropogenic, or microplastic. Items
determined to be microplastics or artificial polymers were
cleaned and made into slides, or placed into small bags if too
large for a slide.
Statistical analysis
Statistical analysis was conducted utilizing SPSS, versions 22.0
and 23.0. Procedures included Crosstabs, Correlation, and
Means.
Description
Orthopristis chrysoptera, commonly known as a grunt, are members of the
family (Haemulidae). Grunt can be found in the Gulf of Mexico from Florida
to the Yucatan peninsula and along the Atlantic coast of the United States
from the southernmost point of Florida to New York. Juvenile grunt reside
within shallow waters close to the shoreline and and prefer habitats which
include dense vegetation. Juvenile grunt feed mainly upon copepods,
shrimp larvae, and mysid shrimp. Adult grunt frequent deeper areas which
are more thinly vegetated and prefer a diet of polychaetes, amphipods, fish
larvae, shrimp, and crabs. Predators of this species include snappers,
groupers, sharks, and spotted seatrout.
ACKNOWLEDGEMENTS
We thank the Gus Glascock Endowment , the Baylor University Research Grant Program, and the
Baylor URSA Undergraduate Research Small Grant Program for providing funds for travel and other
expenses for this project. We thank Colleen Peters for assistance with field collection and analysis.
Recent related article: Peters, C.
A., S.P. Bratton. 2016. Urbanization
is a major influence on
microplastic ingestion by sunfish in
the Brazos River Basin, Central
Texas, USA. Environmental
Pollution. 210:380-387.
MORPHOLOGY & INGESTION BY SIZE
 The mean length of grunt was 17.31cm. The mean weight was 77.94g
and the mean stomach weight was 1.00g
 The overall mean frequency of grunt that had ingested microplastics or
anthropogenic fibers was 29%
 The mean number of particles per fish was 1.43
 Neither frequency of ingestion nor number of particles ingested was
correlated with fish length, overall weight, or stomach weight
 Grunt primarily ingest small crustaceans and mollusks.
 The most dominant microplastic color was blue
 The majority of the particles in these marine samples were thread
shaped or elongated. Spheres or cubes were uncommon. For the grunt,
98% of the particles were threads and 2% were microbeads (Fig.6).
Threads may become entangled in natural foods or may be more
difficult to expel. This suggests incidental ingestion of anthropogenic
materials.
 Despite hypotheses in the literature that marine fish may mistake fibers
for prey species such as worms, preliminary inspection of the stomach
contents did not suggest that grunt were selectively foraging on fibers.
GOALS
1. Determine if a coastline marine fish species ingest
microplastics or artificial polymers.
2. Determine if fish length and weight influence levels of
microplastic ingestion.
3. Classify the main forms of particles ingested.
Fig. 4. Pearson product moment correlations among sample means for
average fish weight, length, and stomach weight, and the percent of
fish with microplastics, and the average number of microplastics per
fish
CONCLUSIONS
• Microplastics are a frequent contaminant in coastal Texas waters
• 29% of fish examined had ingested microplastics, which is similar to results
reported in other marine studies (12-37%) (Sanchez et al., 2014)
• 98% of microplastics were in the shape of threads and the majority were blue
in color
• The presence of Cymothoa exigua did not correlate to the frequency or
number of microplastics ingested
• Microplastic ingestion did not correlate to fish length, weight, or stomach
weight
• The greatest frequency of microplastic ingestion occurred at Surfside Jetty
(61%), followed by the Freeport Channel (24%), both of which are located at
the mouth of the Brazos River
• Based on the results of Peters and Bratton (2016), we suggest the following
hypothesis: Microplastic ingestion is greater at Surfside Jetty and Freeport
Channel due to a greater proportion of microplastics residing within the
Brazos River and releasing into the Gulf of Mexico
0.2
0.61
0.14
0.24
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
91st Surfside Jetty San Luis Pass Freeport Channel
MicroplasticFrequency
Sample Location
Figure 3: Overall Microplastic Frequency per Sample Location Figure 6: Mean Number of Microplastics per Fish by Location
1.25
1.65
1
1.33
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
91st Surfside Jetty San Luis Pass Freeport Channel
MeanNumberofMicroplastics
Sample Location
4%
47%
19%
2%
26%
2%
Red
Blue
Gray
Tan
Other
Bead
Figure 7: Distribution of Microplastic Colors
Fig. 1. Sample Locations Along the Texas Gulf Coast
Fig. 2. Typical fiber extracted from stomach content
Figure 5: Cymothoa exigua located on the tongue of a
grunt
The Cymothoa exigua or more
commonly known as the “tongue
eating louse” was found in 20
(16.4%) of the samples. A total of 25
louse were removed from samples,
six had taken the place of the tongue
and eighteen were located in the
gills. Neither the presence nor the
location of the louse correlated with
the frequency or number of
microplastics ingested .
Characteristics:
Dorsal Fin: 12-13 spines followed by 15-16 soft rays
Anal Fin: 3 spines followed by 12-13 soft rays
Both Fins: covered by a deep, scaly sheath
Body Color: light blue-gray, scales have bronze spots on edges which extend
along body to form stripes
Head Color: covered with bronze spots
Fin Color: yellowish bronze with dusky margins
Source: Todayifoundout.com
Source: Investigacion.izt