Map of study sites
We evaluated the distribution of spat and fouling organisms biweekly at 13 sites using PVC settlement plates.
13 sites were selected based on proximity to the inlets, bottom type, bathymetry, historical water quality data, and expert recommendations. Three of the sites are also current or historical monitoring sites for National Park Service, MD Department of Natural Resources, and the MD Coastal Bays Program.
Spatial distribution of spat
This figure illustrates the spatial distribution of spat at each site. The y-axis is the total number of spat and spat scar counts during the field season and the x-axis are the sites ordered from north to south.
The DNR pier site across from Ocean City Inlet and the Wachapreague pier site had the greatest settlement. In general, oysters settled at sites near the inlets - Ocean City Inlet in the north and Chincoteague Inlet in the south.
Temporal distribution of spat
This figure illustrates the temporal distribution of spat at each site. The y-axis is the total number of spat and spat scar counts and the x-axis is the approximate date the plates were collected.
Wachapreague had the earliest settlement peak in comparison to the MCB sites; the peak started in late June.
The peak time was the same for DNR pier, Island Mark 12, and Queen Sound. There were two clear settlement peaks for Guys Point, one in mid July and another one in early August. In general, peak spat settlement, fell within the typical time period between late June and July.
Spatial distribution of fouling species
This figure illustrates how the fouling communities changed spatially. Each color represents a different fouling animal. Barnacles are represented in green, serpulid worm tubes in red, and the three species of bryozoans in yellow, blue, and purple. The y-axis is the percent occurrence of each fouling organism and the x-axis are the study sites ordered from north to south.
There are patterns among the fouling communities. For instance, barnacles are most prevalent at sites further away from the inlets (sites DNR Pier and Queen Sound). The fouling communities shift in southern Chicnoteague Bay near Chincoteague Inlet at Queen Sound, where the bryozoan Bugula neritina is most prevalent.
The unique fouling communities are a result of the environmental parameters such as temperature, dissolved oxygen, pH as well as the hydrodynamics of the MCBs.
Temporal distribution of fouling species
This figure illustrates the temporal distribution of fouling species at each site. The y-axis are the scaled counts, meaning the actual counts of each species (which were very high or very low values) were converted to a similar scale so all of the species could be visualized on one plot. The x-axis is the approximate date the plates were collected.
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If the count values were not standardized, then the y-axis would range from 0 to 2,500 and there would be very high counts for barnacles but very low counts for the bryozoan Microporella. To allow both extremes to be visualized proportionally, the counts were standardized.
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Barnacles and the bryozoans C. tenussimum and B. neritina decreased throughout the season, while worm tubes and the bryozoan Microporella spp. increased.
Fouling communities
This is a non-metric multidimensional scaling plot I made in R that represents the similarities and dissimilarities among sites. To make the visualization clearer, I picked 7 of the 13 sites -- two in the upper, mid, and lower bays plus the Wachapreague control site.
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Each point represent a species composition or community within a site and the colors correspond to the sites shown in the map to the right. Only the distance between the points are relevant so the x and y-axes are arbitrary.
The NMDS plot show the similarities and dissimilarities among sites (shown as ellipses) based on distance. For example, if two ellipses are close or overlap, it means that similar species were found at those sites. In other words, the closer the ellipses are, the more similar their species composition.
The ellipse for Wachapreague in black, is far away from the overlapping group on the right, meaning Wachapreague has a different species composition than the overlapping sites. However, the Wachapreague and Queen Sound ellipses overlap, meaning they have a similar species composition. This makes sense, because if you recall from the previous figure, those two sites primarily had the bryozoan Bugula neritina, which was not as prevalent at the other sites.
