Cox2 community barcoding at Prince Edward Island reveals long-distance dispersal of a downy mildew species and potentially marine members of the Saprolegniaceae

Marine oomycetes are highly diverse, globally distributed, and play key roles in marine food webs as decomposers, food source, and parasites. Despite their potential importance in global ocean ecosystems, marine oomycetes are comparatively little studied. Here, we tested if the primer pair cox2F_Hud and cox2-RC4, which is already well-established for phylogenetic investigations of terrestrial oomycetes, can also be used for high-throughput community barcoding. Community barcoding of a plankton sample from Brudenell River (Prince Edward Island, Canada), revealed six distinct oomycete OTU clusters. Two of these clusters corresponded to members of the Peronosporaceae—one could be assigned to Peronospora verna, an obligate biotrophic pathogen of the terrestrial plant Veronica serpyllifolia and related species, the other was closely related to Globisporangium rostratum. While the detection of the former in the sample is likely due to long-distance dispersal from the island, the latter might be a bona fide marine species, as several cultivable species of the Peronosporaceae are known to withstand high salt concentrations. Two OTU lineages could be assigned to the Saprolegniaceae. While these might represent marine species of the otherwise terrestrial genus, it is also conceivable that they were introduced on detritus from the island. Two additional OTU clusters were grouped with the early-diverging oomycete lineages but could not be assigned to a specific family. This reflects the current underrepresentation of cox2 sequence data which will hopefully improve with the increasing interest in marine oomycetes.

A DNA metabarcoding approach for recovering plankton communities from archived samples fixed in formalin

Plankton samples have been routinely collected and preserved in formalin in many laboratories and museums for more than 100 years. Recently, attention has turned to use DNA information from formalin-fixed samples to examine changes in plankton diversity over time. However, no molecular ecological studies have evaluated the impact of formalin fixation on the genetic composition of the plankton community structure. Here, we developed a method for extracting DNA from archived formalin-preserved plankton samples to determine their community structure by a DNA metabarcoding approach. We found that a lysis solution consisting of borate-NaOH buffer (pH 11) with SDS and proteinase K effectively cleaved the cross-link formed by formalin fixation. DNA was extracted from samples preserved for decades in formalin, and the diatom community of the extracted DNA was in good agreement with the microscopy analysis. Furthermore, we stored a plankton sample for 1.5 years and demonstrated that 18S rRNA gene community structures did not change significantly from non-formalin-fixed, time-zero samples. These results indicate that our method can be used to describe the original community structure of plankton archived in formalin for years. Our approach will be useful for examining the long-term variation of plankton diversity by metabarcoding analysis of 18S rRNA gene community structure.

The Effects of Sodium Percarbonate Generated Free Oxygen on Daphnia—Implications for the Management of Harmful Algal Blooms

Increasing frequencies and durations of harmful algal blooms are a nuisance in many aquatic ecosystems. This has led to the use of a variety of control methods to prevent their appearance or to disperse them following their establishment. Most of these methods are not selective; consequently, research into alternative selective methods has been ongoing. Reactive oxygen species generated following the addition of hydrogen peroxide have been shown to selectively target the cyanobacterial component of harmful algal blooms in experimental and field settings. This study assesses the effects of increasing concentrations of reactive oxygen species from the addition of sodium percarbonate on zooplankton in a small experimental setting using a natural plankton sample. It was found that the genus Daphnia showed moderate sensitivity to sodium percarbonate. Preliminary evidence suggests that the size of an individual may affect the probability of survival, with larger individuals having a lower likelihood of survival. Lower survival rates of large Daphnia were hypothesized to have been caused by higher relative filtration rates of larger individuals. From the zooplankton data obtained, we suggest that a safe concentration of sodium percarbonate for Daphnia individuals would be below 10.0 mg·L−1 sodium percarbonate (2.8 mg·L−1 hydrogen peroxide).

Two new species of the genus Caligus (Crustacea, Copepoda, Siphonostomatoida) from the Sea of Japan, with a note on the establishment of a new species group

Two new species of Caligus are described from the Japanese coast of the Sea of Japan. Caligus chinglonglinisp. nov. is based on a male specimen found in a plankton sample, whereas C. kajiisp. nov. was collected from the body surface of the host flathead Platycephalus sp. These two new species can be assigned to a distinct species group, the pseudorhombi group newly named and defined by the morphology of the genital complex in both sexes, and by the structure and armature of legs 2 and 4. The species group so far accommodates 19 species including these two new species. The morphology, host specificity and zoogeography of the species group are discussed herein and keys to species groups of Caligus and to species of the C. pseudorhombi species group are provided.

STRUKTUR KOMUNITAS PLANKTON PERMUKAAN PADA DANAU LABUAN CERMIN KEC. BIDUK-BIDUK, KAB. BERAU

This study aims to determine (physico-chemical) parameters of water and also community structure of plankton surface in natural tourism Labuan Cermin Biduk-Biduk, Berau, Kalimantan Timur. This study used Purposive Sampling method. Data obtained shows in plankton abundance, diversity index, evenness index and dominance index. The result of study showed that range of temperature between 24,04 oC -26,88 oC, range of salinity between 0.25-0.87o/oowhich classified in freshwater-brackish water, range of power flow between 1.121-2.930 m/s which classified in moderate level, the average pH between 6,76-7,48 which classified in neutral level, range of TDS between 514-788 mg/L which classified in normal level, respectively. Plankton sample showed 27 classes including of 22 classes of phytoplankton with 57 genera and 5 classes of zooplankton with 10 genera. The highest total plankton abundances of 35917 ind/L is in Station A and the lowest total plankton abundances of 8330 ind/L is in Station F. Keywords: Plankton, Labuan Cermin, Diversity.

Makanan dan pertumbuhan ikan bandeng, Chanos chanos (Forsskal, 1775) tebaran di Waduk Sermo, Kulon Progo [Food and the growth of introduced milkfish, Chanos chanos (Forsskal, 1775) in Sermo Reservoir, Kulon Progo]

The purpose of the research was to study feeding preferences and the growth of milkfish introduction into Sermo reservoir Kulon Progo regency. Research was carried out by introduction of milkfish juvenile which body length was ranges of 5-7 cm and weight of 0.6-1.0 g at a number of 10,000 individual fish. Fish sampling using gill nets was conducted monthly from May to October 2015. The captured milkfish brought to the laboratory for some measurements i.e length and weight of an individual fish, intestine length, and gut content investigation. The surface water plankton sample collected by a plankton net, then preserved in formaldehyde, identified and counted the number each plankton species. Data were analyzed to determine relative gut length, food type and feeding preferences, growth rate and length weight relationships. The results showed that relative intestinal length was 5.4 to 6.4, so milkfish categorized as herbivores. Phytoplankton was the only food found in the intestine fish size <14 cm, while zooplankton was found in fish size >15 cm. Zooplankton proportion in digestive tract increased as well as the size of milkfish. The dominant species of phytoplankton found in the digestive tract was Nitzschia sp., whereas zooplankton was Cyclop sp. and Diaptomus sp. The juvenile milkfish growth well in Sermo reservoir. The growth rate of daily length was ranged from 0.0084 to 0.2056 cm, while the growth rate of daily weight ranged from 0.0630 to 1.1182 g. The length weight relationship of milkfish formed an equation W = 0.0069 L 3 0186 with the regression index R2 = 0.98, so the growth of milkfish showed an isometric growth pattern. Further research is needed to determine the impact of the introduction of milkfish to the fish communities in the Sermo reservoir area.AbstrakTujuan penelitian adalah untuk mengkaji makanan dan pertumbuhan ikan bandeng tebaran di waduk Sermo Kabupaten Kulon Progo. Penelitian dilakukan dengan menebar yuwana ikan bandeng yang panjang tubuh berkisar 5-7 cm dan bo-bot 0,6-1,0 g ke perairan Waduk Sermo sebanyak 10.000 ekor. Sampling ikan bandeng menggunakan jaring insang dilakukan tiap bulan sekali dari Mei sampai Oktober 2015. Ikan bandeng yang terjerat jaring dibawa ke laboratorium untuk diukur panjang, ditimbang bobot individu, dan dilakukan pembedahan untuk diambil saluran pencernaannya. Sampling plankton dilakukan dengan mengambil air permukaan menggunakan ember dan menyaring dengan plankton net, kemudian diawetkan dalam larutan formalin hingga identifikasi dan penghitungan jenisnya. Data dianalisis untuk me-nentukan jenis makanan dan pemilihan makanan, laju pertumbuhan, panjang usus relatif, dan hubungan panjang bobot. Hasil penelitian menunjukkan panjang usus relatif ikan bandeng sebesar 5,4-6,4 yang dikategorikan sebagai ikan herbi-vora. Jenis makanan yang ditemukan pada ikan berukuran <14 cm hanya fitoplankton, sedangkan zooplankton ditemu-kan pada ikan yang berukuran >15 cm. Proporsi zooplankton pada usus ikan semakin banyak seiring ukuran ikan bandeng. Jenis fitoplankton yang ditemukan dominan pada saluran pencernaan adalah Nitzschia sp., sedangkan zooplankton adalah Cyclop sp. dan Diaptomus sp. Yuwana ikan bandeng dapat tumbuh baik di kawasan Waduk Sermo. Laju pertumbuhan panjang harian berkisar 0,0084 - 0,2056 cm, sedangkan laju pertumbuhan bobot harian berkisar 0,06301,1182 g. Hubungan panjang bobot ikan bandeng membentuk persamaan W=0,0069 L 3,0186 dengan indeks regresi R2=0,98, sehingga ikan bandeng cenderung memiliki pola pertumbuhan isometrik. Penelitian lebih lanjut diperlukan untuk mengetahui dampak introduksi ikan bandeng pada komunitas ikan di Waduk Sermo.