The Properties Of Marine Colloids And Their Influence On Micro-algal Growth

In this thesis, cross-flow ultrafiltration have been used to isolate marine colloids,We studied the effect of marine colloidal substance on the growth of micro-algalduring Rhizosolenia delicatula bloom in Jiaozhou Bay; simulated cultivationexperiments in the lab were conducted to evaluate the properties of colloidalsubstances in micro-algal culture medium and their effects on micro-algal growth;in addition, two algal were cultured to test weather phytoplankton are a directresource of dissolved organic matter fluorescence. The main results read as follows:1. Surface water samples were collected in the Jiaozhou Bay where The Rhizosolenia delicatulabloom was observed. The samples were separated into retentate and permeate usingcross-flow ultrafiltration (1kDa). The Heterosigma akashiwo and Skeletonema costatum werecultured in 0%, 50%, 100% proportion of retentate and permeate to study the effect ofcolloidal substance on Microalga growth during R. delicatula bloom in Jiaozhou Bay. Theresults suggested that: the colloidal substances in R. delicatula bloom water canenhanc the growth of H. akashiwo but suppress the growth of S. costatum. Thepromotion and suppression reinforced with the increase of colloid amount. TheLogistic growth model proved a clear and precise description of the cultivationperiod of H. akashiwo and S. costatum, the max growth rate and max cellcalculated by Logistic growth model suggested that R. delicatula can produce anallepothetic substance which promote H. akashiwo growth and suppress S.costatum growth.2. In the present study, colloid concentrates were obtained by using cross-flow filtration system to ultrafiltrate the culture medium of H. akashiwo and S.costatum (which were pre-filtrated by GF/F membrane) successively with three membranes. Fluorescence spectra, dissolved organic carbon(DOC) and total carbohydrate (TCHO) in the pre-filtrate and three retentions and permeates were examined. Then, another micro-algal were cultivated in the pre-filtrate, threeretentions(100kDa-0.7nm, 10-100kDa, 1-lOkDa) and the permeate (lkDa) in the culture medium of// akashiwo. And 12.64 percent of DOC existed in the colloids in the culture medium of S. costatum.(2) Protein-like and humic-like fluorescence peaks were found in the fluorescence spectra of the filtrate of H. akashiwo and S. costatum. Through the comparison of fluorescence spectra between retentions and permeates, we found that a part of protein-like fluorescence substance exist in the colloidal concentrations, the humic-like fluorescence substance existed mainly in the permeate.(3) A great deal of carbohydrate existed in the culture medium of H. akashiwo, about 31.97 percent of TCHO was colloidal saccharides(CCHO)(>lkDa) . In the secretion of S. costatum, there was 8.09 percent of TCHO was colloidal saccharides(CCHO)(>lkDa).(4) H. akashiwo can secrete a kind of substance which can restrain the growth of S. costatum intensively, hi the colloidal retention of 10-100kDa and l-10kDa, S. costatum didn't grow absolutely. The growth rate of S. costatum in the colloidal retention of 100kDa-0.7um was slower than the pre-filtrate and permeate.(5) Substance secreted by S. costatum also can restrain the growth of H. akashiwo intensively. In the pre-filtrate and colloidal retention of 100kDa-0.7 urn, H. akashiwo didn't grow absolutely. The growth rate of//, akashiwo in the colloidal retention of 10-100kDa was slower than the colloidal retention of l-10kDa and the permeate.3. H. akashiwo and S. costatum were cultured to observe the change of fluorescenceduring the growth of the algal, the main results read as follows: (1) Protein-like and humic-like fluorescence increased with growth of//, akashiwo, there were a rapid increases of fluorescence substance in the stationary phase; inthe exponential phase of S. costatum, there were no significant increase of fluorescence, and Protein-like and humic-like fluorescence appeared until the cell number decreased.(2) Protein-like and humic-like fluorescence were significantly correlated with cell number of the exponential phase of H. akashiwo; there were positive correlation in the exponential phase and negative correlation in the contabescence phase between fluorescence and S. costatum cell number. This results suggested that some micro-algal can produce some fluorescence substance in their process of growth, and fluorescence also can be produced by bacteria using non-fluorescent organic matter derived from phytoplankton .