The influence of vegetation on oxygen and pH levels.

Plants influence (and are influenced by) many chemical compounds and nutrients. Two of the crucial chemical characteristics they influence are the levels oxygen and the pH (the acidity of the water).

Oxygen dissolved within the water are as important to aquatic creates as it is to us.  Like plants on land, aquatic plants photosynthesise which produces oxygen, only they emit oxygen into water as opposed to the atmosphere. However, a feature that is often overlooked is the fact that plants respire too. As a result, photosynthesis dominates during the hours of sunlight leading to higher oxygen levels. However, during the hours of darkness, respiration (of the plants and animals) removes oxygen from the water at night. This leads to a pattern like this:

Figure 1: The effect of plants on oxygen and pH of water.  (Jackson Bottom Wetlands Reserve, 2014).

Therefore, the introduction of plants in restoration schemes requires caution, for example plants introduced in shaded regions will reduce oxygen levels, not increase it! Furthermore, a process known as 'eutrophication' is one of the most significant pollution events that occurs within rivers. It is simply excessive plant growth which has been known to reduce oxygen levels to dangerously low levels and kill animals. 

Although changes in the oxygen and pH will change with the time of year, plant species and amount of vegetation, these patterns are easy to measure at home, as demonstrated by the home experiment 3.

This home experiment involves purchasing some form of aquatic vegetation and leaving this within a container filled with water. The amount of vegetation/water used is subjective and could be worth using different levels of each to see how this affects the results. The test kits are commercially available and many fish tank owners will already possess the equipment needed.

It involves simply taking readings of the oxygen and pH over a 24 hour period. The more often you collect measurements, the more reliable your data will be. It is useful for people who keep fish as a hobby to conduct this within the tank to see if oxygen levels are to a satisfactory level 24 hours a day (above 5mg/l as a minimum). 

Bibliography

ISECA (2013) 'What is eutrophication?' http://www.iseca.eu/en/science-for-all/what-is-eutrophication

Jackson Bottom Wetlands Reserve (2014) 'Aquatic chemistry overview' http://www.jacksonbottom.org/monitoring-restoration/aquatic-chemistry-overview/

The importance of in-stream tree matter.

Without researching, tree matter (or woody debris) may seem like a simple issue, but its influence on ecology is significant. It has:

·      An enhanced effect on the connectivity with the floodplain, which is key for nutrient input and flow shelter of animals during high flows.

·   A direct influence on the quality of spawning sites for some species (such as the ‘logjammer hoverfly’).

·      An indirect influence on the quality of spawning sites for some species (such as the removal of fine sediments enhancing salmon reproduction).

·      An overall enhancement on habitat quality by providing shelter from fast flows.

Figure 1 – A fish sheltering under a tree (Mott, 2006. Page 5). 

Although demonstrating its influences on specific species cannot be done using basic home experiments, the clip below shows how it influences the top and bottom points. 

 

 

Bibliography

 

Mott. N (2007) 'Managing woody debris in rivers, streams and floodplains'  http://therrc.co.uk/MOT/References/WT_Managing_woody_debris.pdf.



The physical complexity of rivers.

In the past, modifications to river systems were mainly conducted to prevent flooding and improve navigation. The extent of such influences means that completely natural river systems are now considered a rarity. These projects mainly involved straightening and deepening rivers, leading to physically simple channels. For example, the most globally reported of these issues is The Mississippi River, which was shortened by 235km and severely deepened across the twentieth century, reducing the overall health of the river. Modified channels often possess a uniform physical structure, with little complexity.

Figure 1 – Typical outline of a modified river system.

Modern restoration projects have combated the reduction in habitat quality induced by human interference by creating physical complexities within the channel. This involves altering the outline of the river by using techniques such as introducing meanders, changing the depth of the water and inputting vegetation and associated features (see woody debris).

Figure 2 – Example of a natural river system.

Changes in depth will naturally occur in all types of river due to changes in erosion and deposition of sediment. These processes lead to formations on the bed (bedforms). Different bedforms exist, ranging from small ripples like those seen on the beach, to mega dunes, like those seen in deserts that are created by the wind. Pools (deep zones) and riffles (shallow zones) are common bedforms and important to living things within the river system. Such features are crucial for fish, such as salmon, which often use riffles for spawning and pools for resting and eating.

Although inputting these natural features influences many aspects of the river system, a crucial (and easy to demonstrate) result is the change in flow. The following home experiment shows this.



Bibliography

 

Friends of the Issaquah salmon hatchery (n.d.) 'Fish habitat needs' http://www.issaquahfish.org/downloads/FISH-Learn-Unit_4.pdf

The RRC (n.d) 'River Skerne: restored 1995/98' http://www.therrc.co.uk/pdf/Publications/skerne_brochure.pdf

USGS (2012) 'A brief history and summary of the effects of river engineering and dams on the Mississippi River system and delta' http://therrc.co.uk/MOT/References/WT_Managing_woody_debris.pdf

Introduction: The importance of rivers.

Rivers are a significant aspect to human life, although many people overlook them. For example, a sustainable water supply is frequently drawn from river basins across the world. Flooding is the most widely reported natural disaster affecting millions of people globally every year. Rivers also significantly boost the economy due to their importance to various groups such as:

·       Nature/ wildlife enthusiasts. 

·        Those undertaking recreational sports, such as kayaking and canoeing.

·   People wanting the protection of local heritage, where the natural beauty may attract tourism.  

·       Energy groups through hydropower.

·        Anglers. 4 million anglers contribute £6 million to the economy in the UK every year.

The health of our rivers has been damaged over the last few centuries due to human intervention. We are now in a state of attempting to recover biodiversity within rivers, which EU setting a deadline of 2015 to achieve this.

This blog introduces some very basic topics when applying restoration and rehabilitation schemes and how you can see this within the comforts of your own home! Note, this is a very brief introduction and would encourage anyone interested to read/look around further.