Estado trófico y estructura comunitaria del microfitoplancton en un sector del golfo de Guayaquil, Ecuador

Abstract

Urban growth in coastal areas has led to eutrophication, which in turn has caused the accumulation of organic in the estuarine system of the gulf of Guayaquil. In this scenario trophic status was determined using the Karydis index in three zones established according to hydrographic affinity one mile from the coastal margin of the province of El Oro. Additionally, multivariate analysis were developed to establish the relationship between micro-phytoplankton and physical and chemical variables. Significant differences in trophic levels and community structure were found in each zone. Zone A (Jambeli channel), had the highest trophic index, nitrate (3.8) and silicate (4.9), and lowest salinity, dissolved oxygen, and transparency; zone B (coastal marine exchange area), the one with the greatest oceanic influence, had medium trophic levels (nitrate: 3.4 and silicate: 4.6); zone C (Puna island), had the highest salinity and lowest trophic indexes (3.2 nitrate and 4.3 silicate). The representative species in zone A were: Nitzschia longissima , Skeletonema costatum , and Pseudonitzschia delicatissima ; zone B: P. delicatissima , Guinardia striata , and Leptocylindrus danicus ; zone C: Paralia sulcata , Thalassionema nitzschioides , and S. costatum . The study area was determined as mesotrophic. However, zone A presented the highest trophic level, probably due to a greater influence from human activities.