TY - BOOK AU - Lagundino,Myrose G. TI - Phytoplankton diversity in the mangrove area of Nagabungan, Pasaquin, Ilocos Norte / PY - 2021/// N1 - Thesis (BS Env’l Sci) – Mariano Marcos State University N2 - ABSTRACT LAGUNDINO, MYROSE G. and MINICOLAS, ROSEVEEH P. 2021. Phytoplankton Diversity in the Mangrove area of Nagabungan, Pasuquin, Ilocos Norte. Undergraduate Thesis. College of Agriculture, Food and Sustainable Development. Mariano Marcos State University, City of Batac 2906 Ilocos Norte. 85pp. Adviser: Prof. Estrelita 0. Domingo The study on the phytoplankton diversity in the mangrove area of Nagabungan, Pasuquin, Ilocos Norte was conducted from February to March 2021 during the two phases of the moon: new moon and full moon. Two sampling sites were identified namely, the natural and planted stands. There were five stations established each in both sampling sites. The study aimed to determine the physico- chemical characteristics of the water in the mangrove area, identify and document the phytoplankton diversity, density, and similarity in the area; and correlate the diversity, density and similarity and the physico-chemical characteristics in the mangrove area. In terms of physico-chemical characteristics in the mangrove area of Nagabungan, Pasuquin Ilocos Norte, the result of the study showed the following results: a) temperature was 26.83 °C; b) depth was 67.5 cm; c) conductivity was 41165 ps/cm. For the chemical characteristics: a) pH was 8.0; b) salinity was 26.32 ppt; and c) Total dissolved Solids was 20580 mg/l. All the parameters measured passed the standards set by DENR DAO 2016-08 for marine fishery waters. A total of 38 different species were observed with a total of 5,956 number of individuals. There were 29 species that were identified but nine species were not identified. Phytoplankton species identified and documented were group into: 10 centric diatom, four pennate diatom, four marine diatom, five dinoflagellates, and six cyanobacteria. Generally, higher population density was recorded during full moon in both the natural and planted sites with 143.7 cells L and 257.0 cells L'', respectively. In new moon, lower population density was observed with the value of 79.4 cells Land 110.8 cells L' in the natural and planted stand, respectively. The Index of Similarity was higher in the natural stand (65%) and in planted stand (69%) during full moon. This means that there were species present during full moon but was not observed during new moon. Correlation analysis showed that there is no significant relationship between species diversity and the physico-chemical parameters (depth, conductivity, salinity, pH, and TDS). However, population density has positive association with depth, temperature and sampling periods but negative association with pH. The similarity index showed highly significant positively association with depth and conductivity, while salinity and TDS was with moderate association ER -