Fungal colonization of immersed wood in mangroves of the southwest coast of India

Abstract

Patterns of fungal colonization during in situ decomposition of woody substrata of two mangrove tree species (Avicennia officinalis L. and Rhizophora mucronata Lamk.) were studied in the Udyavara mangrove forest in the west coast of India. Wood pieces detached from the terrestrial parts of trees were packed in litter bags and introduced into the mangrove habitat at low tide. Samples were retrieved at different intervals for up to 18 months. They were scanned for fungi following incubation in the laboratory for up to 6 months on a sand bath with sterile mangrove water collected on each sampling date. Temperature, pH, oxygen, and salinity of water were assessed at each sampling date to relate to the colonization of fungi on wood. Forty-five species of fungi comprising 20 ascomycetes and 25 anamor phic taxa were recovered. Aigialus mangrovei Borse, Cirrenalia pygmea Kohlm., Cirrenalia tropicalis Kohlm., Lignin cola laevis Höhnk, Lulworthia sp., Savoryella paucispora (Crib et J.W. Cribb) J. Koch, Tirispora sp., Trichocladium achrasporum (Meyers et R.T. Moore) Dixon, and Verruculina enalia (Kohlm.) Kohlm. et Volkm.-Kohlm. were the core group (frequency of occurrence, ≥10%) Avicennia officinalis wood. Aigialus mangrovei, Ascosalsum cincin natulum (Shearer et J.L. Crane) J. Campb., J.L. Anderson et Shearer, Cirrenalia pygmea, Cirrenalia tropicalis, Lul worthia grandispora Meyers, Tirispora sp., and Verruculina enalia were the core group on R. mucronata wood. On both wood types, distinct peaks were seen in richness, diversity, and core-group fungi after 2, 10, and 14 months of immersion. Avicennia officinalis yielded a higher number of fungi in most of the samples than did R. mucronata. Within 2 months, typical marine fungi replaced the terrestrial fungi on the wood because of increased salinity. The number of fungi recorded in the month of August (monsoon season) was highest. Most of the additional fungi were terrestrial fungi that colonized the wood because of a decline in salinity. The pattern of fungal colonization with respect to early, late, and persistent colonizers was similar in both types of wood. Instead of differing in fungal species, the frequency of colonization of fungi differed on Avicennia officinalis and R. mucronata wood, which indicates substrate recurrence rather than specificity.Key words: colonization, diversity, filamentous fungi, mangroves, seasonal occurrence, woody litter.