in sediments. Plants produce pollen in large quantities and it is extremely resistant to decay. It is possible to identify a plant species from its pollen grain. The identified plant community of the area at the relative time from that sediment layer, will provide information about the climatic condition. The abundance of pollen of a given vegetation period or year depends partly on the weather conditions of the previous months, hence pollen density provides information on short-term climatic conditions. The study of prehistoric pollen is palynology. Dinoflagellate cysts Dinoflagellates occur in most aquatic environments and during their life cycle, some species produce highly resistant organic-walled cysts for a dormancy period when environmental conditions are not appropriate for growth. Their living depth is relatively shallow (dependent upon light penetration), and closely coupled to diatoms on which they feed. Their distribution patterns in surface waters are closely related to physical characteristics of the water bodies, and nearshore assemblages can also be distinguished from oceanic assemblages. The distribution of dinocysts in sediments has been relatively well documented and has contributed to understanding the average sea-surface conditions that determine the distribution pattern and abundances of the taxa (). Several studies, including and have compiled box and gravity cores in the North Pacific analyzing them for palynological content to determine the distribution of dinocysts and their relationships with sea surface temperature, salinity, productivity and upwelling. Similarly, and use a box core at 576.5 m of water depth from 1992 in the central Santa Barbara Basin to determine oceanographic and climatic changes during the past 40 kyr in the area. Lake and ocean sediments Similar to their study on other proxies, paleoclimatologists examine oxygen isotopes in the contents of ocean sediments. Likewise, they measure the layers of varve (deposited fine and coarse silt or clay) laminating lake sediments. Lake varves are primarily influenced by: Summer temperature, which shows the energy available to melt seasonal snow and ice Winter snowfall, which determines the level of disturbance to sediments when melting occurs Rainfall Diatoms, foraminifera, radiolarians, ostracods, and coccolithophores are examples of biotic proxies for lake and ocean conditions that are commonly used to reconstruct past climates. The distribution of the species of these and other aquatic creatures preserved in the sediments are useful proxies. The optimal conditions for species preserved in the sediment act as clues. Researchers use these clues to reveal what the climate and environment