Exploring Fungal Diversity Through The Recent Past: New Laboratory and Educational Approaches

To disentangle human disturbances recorded in non-consolidated sediments, this research uses coprophilous fungal remains as proxy of pastoralism and defaunation at the spatial scale of a watershed. A new protocol for examining coprophilous fungal conidiospores in lacustrine sediments was tested and calibrated using tropical lacustrine sediments and herbivore’s dropping samples. Finally, we present an online activity that uses fungal remains to teach middle schoolers ecosystem's matter and energy cycles with superficial soil samples from the Western US using this new lab procedure. 

Traditional protocols to prepare Non-Pollen Palynomorphs (NPP’s) in paleoecology and palynology can degrade fungal remains or even mask translucent remains. Improved methods for uncovering fungal remains are needed to allow fungi proxies to be used for detecting and understanding past disturbances. The new laboratory protocol allows for the recovery of fungal remains based on the physical separation of the sediment components, using fewer non-toxic reagents and reducing the overall lab expenses. This, in turn, makes the method more accessible in countries with limited equipment and reagents accessibility such as Colombia. The protocol prioritizes physical separation over chemical procedures to avoid adverse effects on fungal remains and toxic waste. The basic protocol entails: (1) Disaggregating soil components using sodium hexametaphosphate; (2) A hot water ultrasonic bath, vortexing, and letting the sample settle; (3) Sieving samples with double mesh (7 µm and 250 µm sizes) sieves to remove very large and very small particles; (4) Centrifuging to separate organic and mineral portions of the remaining sediment; (5) and lastly, staining the subsample using Lactophenol Cotton Blue (targets translucent fungal remains made out of Chitin). This new protocol is less corrosive than traditional methods since all separation steps emphasize physically splitting sediment components. Ongoing testing will establish the degree to which this new protocol reduces biases in studying fungal remains. The diversity of fungal conidiospores found in tropical lacustrine sediments (top 20 cm) of San Diego Lagoon (SDL core Fc2) is partial proof that this new method works properly to extract NPP’s from lacustrine sediments where at least 77 types of conidiospores and other fungal remains were identified and at least 16 of them are ecologically informative. 

Keywords: Non-pollen palynomorphs; fungi; palynology; education; ecological disturbances.