2017 Lake Worth Lagoon Benthic Community Study Permanent Seagrass Transects. Preliminary Results

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1 2017 Lake Worth Lagoon Benthic Community Study Permanent Seagrass Transects Preliminary Results

2 2016 Benthic Study Objectives The main objective of the 2016 CAP 1135 study was to compare softbottom benthic communities of constructed environmental restoration projects with impacted submerged lagoon bottom, comparing intertidal restored habitats with subtidal mucky bottom. The study did not examine differences between subtidal unvegetated mucky bottom and subtidal vegetated habitat in the lagoon.

3 Study Design 5 restoration project locations 5 natural, impacted locations (candidate restoration sites) 10 locations- 20 sites

4 2016 Study Results Bivalves were the most abundant class at both impacted and restored locations, but heavily dominated the impacted locations at 95%. Six of the ten impacted sites were muck bottom while all ten restored sites were predominantly sand. The site with the deepest muck layer and highest organic content, Bonefish Cove 16, had the lowest overall macrofaunal abundance and diversity. Taxonomic richness was higher at the impacted sites due to the dominance of bivalves and polychaetes. Malacostracans, which include tanaids, cumaceans, amphipods, and fiddler crabs, were only found at the restored locations in this study.

5 2016 Benthic Study Results The 2016 benthic study results demonstrated the importance of remediating sediment habitat in the central lagoon to increase benthic community richness. However, all sites are subjected to similar water quality stressors in the central lagoon, such as large freshwater influxes and unstable salinity, which has been shown to be a controlling factor in bivalve assemblages in the Indian River Lagoon/St. Lucie Estuary.

6 LWL Fixed Seagrass Transect Program Main objective is to document annual changes in seagrass abundance and distribution at the permanent transects as an indicator of lagoon-wide seagrass health. Each transect consists of three 1-m 2 permanent stations monitored for species presence/absence and Braun-Blanquet cover estimates. In 2017, seagrass was only recorded at 2 of the 9 historic transects, Transects 1 and 10. Transects 11 and 12 supported the greatest seagrass cover and diversity during the surveys. Transect 11 is the only permanent transect to document Thalassia testudinum.

7 Benthic Study Methods Benthic macrofauna samples- 10 cm x 10 cm PVC cores, sieved with 0.5 mm mesh. Restoration and impact sites- 5 cores/site; 2 sites per location Seagrass Transects- one core/permanent station; 3 cores/transect to calculate mean density

8 Total seagrass frequency of occurrence at the ten permanent seagrass transects, Transect Sep 2006 June 2007 July 2008 May 2009 June 2010 June 2011 July 2012 July 2013 July/Aug Aug July/Aug July/Aug Transect Transect Transect Transect Transect Transect Transect Transect Transect Transect

9 Bonefish Cove Bryant Park South Currie Park El Cid Snook East Bryant Park West Grassy Flats Ibis Snook South Cove Phil Foster Peanut Island Providencia Monceaux Summa Comparison of abundance/density benthic study sites and 2017 seagrass transects Density (#/m 2 ) 0 Highest density/abundance found at Transect 5- highest density followed by Transect 11 Nematodes drove abundance at Transect 5 Polychaetes and nematodes were the dominant groups at Transect 11 Transect 11 in Munyon Cove had highest diversity and richness of all transects

10 Sites Transects Richness S-W Diversity SG Transects Impacted Sites Supplemental Impacted Bonefish Cove Bryant Park South Currie Park El Cid Snook East Phil Foster Peanut Island Providencia Monceaux Summa Diversity Comparisons Seagrass Transects vs Unvegetated Softbottom and Intertidal Restored Sites

11 Mean density (# ind/m2) by lagoon segment and individual transect North segment transects had highest overall abundance of the three segments

12 In contrast, invertebrate density ranged from a low of invertebrates/m 2 at Bryant Park South to a high of invertebrates/m 2 at El Cid at the 2016 impact sites. At the restored locations, invertebrate density ranged from a low of invertebrates/m 2 at South Cove to a high of 1, invertebrates/m 2 at Snook Islands.

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14 North segment transects- all 3 transects had seagrass in 2017 Transect Transect Taxon Name Abundance Density (#/m 2 ) Percent Taxon Name Abundance Density (#/m2) Percent S Apionsoma sp N Nematoda A P Capitellidae A P Ctenodrilidae A P Syllidae D P Paraonidae A P Lumbrineridae A P Capitellidae A N Nematoda A P Syllidae E Transect Taxon Name Abundance Density (#/m2) Percent N Nematoda A P Maldanidae B P Ctenodrilidae A P Capitellidae F P Capitellidae A Transect Sep 2006 June 2007 July 2008 May 2009 June 2010 June 2011 July 2012 July 2013 July/Aug Aug July/Aug July/Aug Transect Transect Transect Transect 1- Dominance of Phylum Sipuncula (peanut worms unsegmented benthic worms) Peanut worms were found mostly in northern lagoon sites by Deis et al. 1983

15 North Segment Transects 1, 11, and 12 Dominance of polychaetes at all 3 transects High abundances of nematodes at Transects 11 and 12 Seagrass beds are home to large amounts of nematodes due to the detritus that builds up in seagrass beds.

16 Similar to the 2016 benthic study, Transect 4 was dominated by bivalves at 75% of the community Transect Transect Taxon Name Abundance Density (#/m2) Percent Taxon Name Abundance Density (#/m2) Percent B Mulinia lateralis N Nematoda A P Ctenodrilidae A Os Cylindroleberididae A P Phyllodocidae A B Mulinia lateralis P Capitellidae C B Corbula swiftiana B Corbula swiftiana P Capitellidae A Transect Transect Taxon Name Abundance Density (#/m2) Percent Taxon Name Abundance Density (#/m2) Percent P Ctenodrilidae A P Ctenodrilidae A B Corbulidae A P Capitellidae A B Mulinia lateralis B Mulinia lateralis P Lumbrineridae B N Nematoda A P Nereididae A B Corbula swiftiana Transect Central Segment Transects Sep 2006 June 2007 July 2008 May 2009 June 2010 June 2011 July 2012 July 2013 July/Aug 2014 Aug 2015 July/Aug 2016 Transect Transect Transect Transect Transect 6- dominance by nematodes. Chaetomorpha linum in 2017 July/Aug 2017 High cover of the filamentous alga

17 Central Lagoon Transects

18 South Lagoon Transects Transect Transect Taxon Name Abundance Density (#/m2) Percent Taxon Name Abundance Density (#/m2) Percent P Ctenodrilidae A N Nematoda A N Nematoda A P Lumbrineridae B M Oxyurostylis smithi P Ctenodrilidae A P Chaetopteridae A Ph Phoronida A Os Cylindroleberididae A P Capitellidae A Transect Taxon Name Abundance Density (#/m2) Percent N Nematoda A P Ctenodrilidae A P Syllidae A P Lumbrineridae B N Nemertia A Transect Sep 2006 June 2007 July 2008 May 2009 June 2010 June 2011 July 2012 July 2013 July/Aug Aug July/Aug July/Aug Transect Transect Transect Transect 5- historically had high cover of seagrass. No seagrass at stations since Transect 5 was characterized by moderate density Lyngbya sp. in 2017

19 South Lagoon Transects

20 Dominant Bivalve and Polychaetes between Impacted sites and Central Lagoon Seagrass Transects Impacted Core Locations Currie Park El Cid Class Family Lowest ID Abundance Density (#/m 2 ) Percent Class Family Lowest ID Abundance Density (#/m 2 ) Percent B Corbulidae Corbula sp. A B Mactridea Mulinia lateralis B Solecurtidea Tagelus divisus B Solecurtidea Tagelus divisus B Veneridae Chione sp B Corbulidae Corbula sp. A Snook East Bryant Park South Class Family Lowest ID Abundance Density (#/m 2 ) Percent Class Family Lowest ID Abundance Density (#/m 2 ) Percent B Mactridea Mulinia lateralis B Solecurtidea Tagelus divisus B Corbulidae Corbula sp. A B Mactridea Mulinia lateralis B Solecurtidea Tagelus divisus P Spionidae Spionidae A Bonefish Cove Class Family Lowest ID Abundance Density (#/m 2 ) Percent P Spionidae Spionidae A B Solecurtidea Tagelus divisus B Mactridea Mulinia lateralis Central Lagoon Transect Transect Class Family Lowest ID Abundance Density (#/m 2 ) Percent Class Family Lowest ID Abundance Density (#/m 2 ) Percent B Mactridea Mulinia lateralis B Mactridea Mulinia lateralis P Ctenodrilidae Ctenodrilidae A B Corbulidae Corbula swiftiana P Phyllodocidae Phyllodocidae A P Capitellidae Capitella sp Transect Transect Class Family Lowest ID Abundance Density (#/m 2 ) Percent Class Family Lowest ID Abundance Density (#/m 2 ) Percent P Ctenodrilidae Ctenodrilidae A P Ctenodrilidae Ctenodrilidae A B Corbulidae Corbulidae A P Capitellidae Capitella sp B Mactridea Mulinia lateralis B Mactridea Mulinia lateralis

21 Mulinia lateralis and Corbula swiftiana were the most common bivalves at the central lagoon seagrass transects. M. lateralis was dominant taxa at Transect 4. Mulinia lateralis and Corbula sp. A were two of the dominant bivalves at impacted lagoon sites in 2016, M. lateralis was present at all five impacted locations and was in the top three species at four of the five locations. The bivalve was not found at Phil Foster and Peanut Island, the two euhaline sites closest to Lake Worth Inlet with the most stable salinity regime. M. lateralis is extremely opportunistic with high fecundity. Dominant organism in surveys of lagoon in 1970s and 1980s.

22 Nematoda (roundworms) were not detected during the 2016 benthic study Nematodes were dominant at Transect 6 (66%) and abundant at Transect 5 (50%) and Transect 10 (30%), Transect 11 (20%), and Transect 12 (22%). Nematodes are mostly deposit feeders. In muddy sediments, nematodes are small with short setae. In sandy bottoms, species are longer with long setae and heavily ornamented cuticles, and are more likely to be captured by larger sieve size of this study. Seagrass beds are home to large amounts of nematodes due to the detritus that builds up in seagrass beds. Apionsoma sp. (Peanut worm, Sipunculid) was dominant taxa at Transect 1, and peanut worms were the second most dominant group (36%). Peanut worms were relatively abundant at several north lagoon sites in the 1983 study.

23 Bivalves made up 75% of Transect 4 and were the second most abundant taxonomic group at Transects 6, 8, and 9 comprising 11%, 31% and 21% of each transect. Polychaetes were the most abundant with more than 50% at both Transects 8 and 9. Malacostracans were more common in the north and south segments seagrass transects and lowest at Central transects. Found in low relative abundance at Transects 6 and 8. Phoronids (horseshoe worms) were found at several seagrass transects in 2017 but were not observed at any sites in Phoronids had been found in high abundance at a site near Lake worth Inlet by Deis et al Ostracods were only observed at Currie Park in 2016-, Two ostracod taxa were found at Currie Park 1 (Family Cylindroleberididae) and Currie Park 2 (Family Sarsiellidae). Ostracods made up 10% of the community at Transects 6 and 2 and 5% at Transect 10 in 2017.

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