The influence of invasive ascidian diets on the growth of the sea star Henricia sanguinolenta

Invasive species can disrupt food webs by altering the abundance of prey species or integrating into the food web themselves. In the Gulf of Maine, there have been a suite of invasions that have altered the composition of the benthic ecosystem. These novel prey species can potentially benefit native predators depending on their nutritional value and relative abundance. We measured feeding instances of the native blood star, Henricia sanguinolenta, and changes in the seasonal abundances of invasive ascidian prey species. Results indicate that H. sanguinolenta forages optimally, as the blood star will prey on invasive ascidians when in high abundance, but feed on other species during periods of scarcity. Further, our study shows that blood stars prey on a wider variety of species than was previously known, such as small bivalves and barnacles. Additionally, we compared growth and reproduction of sea stars fed different combinations of invasive ascidians (Diplosoma listerianum or Botrylloides violaceus) or a native sponge (Haliclona oculata). Sea stars grew more on the native diet when compared with the invasive ascidian species, and D. listerianum appeared to be a superior quality food source when compared with B. violaceus. By comparing our data with historical data, we determined that there was a dramatic increase in sea star populations between 1980 and 2011, but then populations decreased by almost half from 2011 to 2016–2017. These data suggest that while invasive ascidians may have helped sea star populations at one point, sea stars are declining without their native food source.

KEPADATAN SPONS PADA EKOSISTEM LAMUN KAITANNYA DENGAN PARAMETER OSEANOGRAFI DI PERAIRAN DESA KASWARI KABUPATEN WAKATOBI

Padang Lamun merupakan tempat hidup bagi beragam organisme, salah satunya adalah spons. Tujuan dari penelitian ini yaitu untuk mengetahui keragaman jenis spons dan lamun di perairan Desa Kaswari Kabupaten Wakatobi serta hubungan kepadatan spons dan persentase tutupan lamun kaitannya dengan parameter oseanografi. Penelitian ini dilaksanakan pada bulan Februari-November 2020 dengan lokasi di perairan Desa Kaswari Kabupaten Wakatobi. Metode Penelitian ini menggunakan metode transek kuadran dengan ukuran 1x1 m. Pengamatan dilakukan di tiga stasiun penelitian yang diambil berdasarkan tipe substrat dasar perairan yang berbeda. Analisis keterkaitan antara kondisi spons dan lamun terhadap beberapa parameter oseanografi dianalisis menggunakan Analisis Komponen Utama (AKU). Hasil penelitian menunjukkan bahwa jenis spons yang ditemukan yaitu Agelas citrina, Agelas conifera, Amphimedon viridis, Clathria reinwardti, Chondrilla caribensis, Haliclona oculata dan Tectitethya crypta. Jenis lamun yang ditemukan yaitu Thalassia hemprichii, Enhalus acoroides dan Cymodocea rotundata. Hasil studi menunjukkan bahwa persentase tutupan lamun sebesar 76.50, 51.83 dan 41.00% memiliki hubungan yang sangat kuat terhadap kepadatan spons sebesar 7.47, 6.17 dan 4.60 ind/m². Semakin tinggi persentase tutupan lamun menunjukkan semakin tinggi kepadatan spons. Parameter oseanografi seperti kecepatan arus memiliki hubungan berbanding terbalik (berpengaruh) terhadap kepadatan spons dan persentase tutupan lamun.Kata Kunci : Spons, lamun, parameter oseanografi, perairan Kaswari, Wakatobi.

BIODIVERSITY ASSESSMENT OF MICROORGANISMS ASSOCIATED WITH TWO MARINE SPONGES (Haliclona oculata AND Amphius huxleyi) COLLECTED AT THE LANG CO BAY OF VIETNAM

Sponges (Phylum Porifera) are ancient sedentary and filter-feeding animals which harbour very diverse and abundant associated microbial community in their tissues with density up to 40–50% of sponge tissue volume. In this study, the diversity of associated microorganisms with two marine sponges Haliclona oculata and Amphius huxleyi collected at the Lang Co bay of Vietnam was assessed by analysis of hypervariable V3 and V4 regions of the 16S rRNA gene using Illumina MiSeq system. The taxonomic diversity of sponge-associated microorganisms was classified to different taxonomic levels (kingdom, phylum, class, order, family, and genus). Based on Bayesian classification method and reference sequences derived from Greengenes database, the associated microorganisms in studied sponges were assigned to 17 phyla (H. oculata) and 13 phyla (A. huxleyi). Many microbial taxa were detected in two sponge species, however, they were distinctive by the abundance. Proteobacteria was the most dominant phylum in both sponge species, and all of 4 classes Epsilonproteobacteria, Gammaproteobacteria, Alphaproteobacteria, and Deltaproteobacteria were found in H. oculata and A. huxleyi.