Lake ecosystem: Difference between revisions

Two important subclasses of lakes are [[pond]]s, which typically are small lakes that intergrade with wetlands, and water [[reservoir]]s. Over long periods of time, lakes, or bays within them, may gradually become enriched by nutrients and slowly fill in with organic sediments, a process called succession. When humans use the [[Drainagedrainage divide|watershedbasin]], the volumes of sediment entering the lake can accelerate this process. The addition of sediments and nutrients to a lake is known as [[eutrophication]].<ref name="Alexander">{{cite book|last=Alexander|first=David E.|title=Encyclopedia of Environmental Science|date=1 May 1999|publisher=[[Springer Science+Business Media|Springer]]|isbn=0-412-74050-8}}</ref>

Lentic systems gain most of their energy from photosynthesis performed by aquatic plants and algae.<ref>{{cite journal |last1=Zhang |first1=Ke |last2=Yang |first2=Xiangdong |last3=Kattel |first3=Giri |last4=Lin |first4=Qi |last5=Shen |first5=Ji |title=Freshwater lake ecosystem shift caused by social-economic transitions in Yangtze River Basin over the past century |journal=Scientific Reports |date=21 November 2018 |volume=8 |issue=1 |pages=17146 |doi=10.1038/s41598-018-35482-5 |pmid=30464220 |url=https://www.nature.com/articles/s41598-018-35482-5 |access-date=13 January 2024 |language=en |issn=2045-2322|hdl=11343/219728 |hdl-access=free }}</ref> This [[wikt:autochthonous|autochthonous]] process involves the combination of carbon dioxide, water, and solar energy to produce carbohydrates and dissolved oxygen. Within a lake or pond, the potential rate of photosynthesis generally decreases with depth due to light attenuation.<ref>{{Cite journal |last=Pirc |first=Helmut |date=January 1986 |title=Seasonal aspects of photosynthesis in Posidonia oceanica: Influence of depth, temperature and light intensity |url=https://linkinghub.elsevier.com/retrieve/pii/0304377086900215 |journal=Aquatic Botany |language=en |volume=26 |pages=203–212 |doi=10.1016/0304-3770(86)90021-5}}</ref> Photosynthesis, however, is often low at the top few millimeters of the surface, likely due to inhibition by ultraviolet light. The exact depth and photosynthetic rate measurements of this curve are system-specific and depend upon: 1) the total biomass of photosynthesizing cells, 2) the amount of light attenuating materials, and 3) the abundance and frequency range of light absorbing pigments (i.e. [[chlorophylls]]) inside of photosynthesizing cells.<ref name="moss:1998"/> The energy created by these primary producers is important for the community because it is transferred to higher [[trophic level]]s via consumption.<ref>{{cite journal |last1=Shimoda |first1=Yuko |last2=Azim |first2=M. Ekram |last3=Perhar |first3=Gurbir |last4=Ramin |first4=Maryam |last5=Kenney |first5=Melissa A. |last6=Sadraddini |first6=Somayeh |last7=Gudimov |first7=Alex |last8=Arhonditsis |first8=George B. |title=Our current understanding of lake ecosystem response to climate change: What have we really learned from the north temperate deep lakes? |journal=Journal of Great Lakes Research |date=1 March 2011 |volume=37 |issue=1 |pages=173–193 |doi=10.1016/j.jglr.2010.10.004 |url=https://www.sciencedirect.com/science/article/abs/pii/S0380133010002091 |access-date=13 January 2024 |issn=0380-1330}}</ref>

[[Eutrophication|Eutrophic]] systems contain a high concentration of phosphorus (~30&nbsp;µgμg/L), nitrogen (~1500&nbsp;µgμg/L), or both.<ref name="bronmark:2005"/> Phosphorus enters lentic waters from [[sewage treatment]] effluents, discharge from raw sewage, or from runoff of farmland. Nitrogen mostly comes from [[Fertilizer|agricultural fertilizers]] from runoff or leaching and subsequent groundwater flow. This increase in nutrients required for primary producers results in a massive increase of phytoplankton growth, termed a "[[Algal bloom|plankton bloom]]." This bloom decreases water transparency, leading to the loss of submerged plants.<ref>{{Cite journal |last1=Birk |first1=Sapriya |last2=Miller |first2=J. David |last3=MacMullin |first3=Aidan |last4=Patterson |first4=R. Timothy |last5=Villeneuve |first5=Paul J. |date=February 2023 |title=Perceptions of Freshwater Algal Blooms, Causes and Health among New Brunswick Lakefront Property Owners |url=https://link.springer.com/10.1007/s00267-022-01736-2 |journal=Environmental Management |language=en |volume=71 |issue=2 |pages=249–259 |doi=10.1007/s00267-022-01736-2 |issn=0364-152X|doi-access=free |pmid=36318287 |pmc=9628596 }}</ref> The resultant reduction in habitat structure has negative impacts on the species that utilize it for spawning, maturation, and general survival. Additionally, the large number of short-lived phytoplankton result in a massive amount of dead biomass settling into the sediment.<ref name="moss:1998"/> Bacteria need large amounts of oxygen to decompose this material, thus reducing the oxygen concentration of the water. This is especially pronounced in [[Lake stratification|stratified lakes]], when the [[thermocline]] prevents oxygen-rich water from the surface to mix with lower levels. Low or anoxic conditions preclude the existence of many taxa that are not physiologically tolerant of these conditions.<ref name="bronmark:2005"/>