355 exam 1 Flashcards

Question

RIPARIAN CANOPY & LEAF LITTER

Answer 1

THE PRESENCE OF A RIPARIAN CANOPY IS IMPORTANT NOT ONLY IN REGULATING THE LIGHT CLIMATE OF STREAMS, BUT ALSO FOR PROVIDING ORGANIC MATER INPUTS IN THE FORM OF LEAF LITTER. * INPUTS OF TERRESTRIAL PLANT MATERIALS SUPPORT SECONDARY PRODUCTION IN STREAM FOOD WEBS.Inputs of organic mater from outside of the ecosystem (e.g., from forest to stream) are referred to as “subsidies”.

Answer 2

Effects of light and nutrient availability on the accumulation of benthic algal biomass in experimental stream channels. Nutrient levels are concentrations of SRP (μg/L). Where there is a loss of canopy shading and elevated nutrient inputs (e.g., urban and agricultural streams) excess growth of stream algae may occur.

Answer 3

* STORMS THAT RESULT IN HIGH DISCHARGE ARE A FORM OF ECOLOGICAL DISTURBANCE (SIMILAR TO FIRES AND BLOWDOWN IN FOREST). * INCREASED WATER VELOCITY SCOURS ALGAE AND SUBSTRATES. * THEIR RECOVERY FOLLOWING DISTURBANCE IS DICTATED BY TEMPERATURE, LIGHT AND NUTRIENTS. FREQUENCY OF STORM EVENTS DICTATES THE IMPORTANCE OF SCOUR VS. GRAZING IN CONTROLLING ALGAL ABUNDANCE * URBAN STREAMS PRONE TO FREQUENT DISTURBANCE DUE TO IMPERVIOUS SURFACES.

Answer 4

LEAVES BECOME WATERLOGGED AND SINK. COLONIZATION BY BACTERIA AND FUNGI BEGINS ALMOST IMMEDIATELY. * SHREDDERS (AQUATIC INSECTS) FRAGMENT LEAVES CREATING MORE SURFACE AREA FOR BACTERIAL DECOMPOSERS.

Answer 5

FRAGMENT LEAVES CREATING MORE SURFACE AREA FOR BACTERIAL DECOMPOSERS. CONVERT COARSE PARTICULATE ORGANIC MATTER (CPOM) TO FINE PARTICULATE ORGANIC MATTER (FPOM).

Answer 6

SCRAPE ALGAE AND BACTERIA FROM LEAVES AND OTHER SURFACES.

Answer 7

CAPTURE FPOM DERIVED FROM TERRESTRIAL (LEAF LITTER) AND INTERNAL (ALGAE) SOURCES.

Answer 8

EAT OTHER INVERTEBRATES

Answer 9

STREAM ORDER: NUMBERS ASSIGNED BASED ON BRANCHING PATTERNS. 1ST ORDER = ‘HEADWATER’ STREAMS (MAY BE EPHEMERAL) 2-4 ORDER: SMALL STREAMS OF INCREASING FLOW. >5TH ORDER: RIVERS OF VARYING SIZE WITH INCREASING STREAM ORDER, STREAMS GET LARGER (GREATER DISCHARGE, ALSO WIDER). WITH GREATER WIDTH, THERE IS LESS RIPARIAN SHADING – LESS LEAF LITTER INPUTS, BUT MORE SUN FOR ALGAE.

Answer 10

Predictable changes in invertebrate functional feeding groups arise from longitudinal variation in organic matter inputs. Headwater streams (low light, high leaf litter): * shredders - take large food (leaves) and produce fine particulate organic matter * collectors - spin nets or use setae to collect FPOM Middle order streams (more light): * scrapers - feed on biofilms Large order streams (more light, lower water velocity) * collectors - collect FPOM from upstream and locally produced phytoplankton

Answer 11

GREEN FOOD WEB: HERBIVORES FEED ON ALGAE AND ARE IN TURN FED UPON BY PREDATORS * BROWN FOOD WEB: DETRITIVORES FEED ON LEAF LITTER AND ARE FED UPON BY PREDATORS IN STREAMS, EXTERNAL INPUTS OF OM (LEAF LITTER) MAY BE MUCH LARGER THAN INTERNAL PRODUCTION (ALGAE)

Answer 12

AUTOCHTHONOUS (INTERNALLY-DERIVED): PRIMARY PRODUCERS IN STREAMS, PRINCIPALLY BENTHIC ALGAE. * ALLOCHTHONOUS (EXTERNAL INPUTS): TERRESTRIAL PLANT PRODUCTION THAT IS EXPORTED TO STREAMS IN DISSOLVED (DOM) AND PARTICULATE (POM) FORMS. * ALTHOUGH AUTOCHTHONOUS OM IS MORE LABILE, ALLOCHTHONOUS OM IS QUANTITATIVELY DOMINANT, PARTICULARLY IN FORESTED STREAMS WHERE THE RIPARIAN CANOPY CONTRIBUTES LEAF LITTER AND SUPPRESSES BENTHIC ALGAE PRODUCTION.

Answer 13

Physical: streamflow (discharge), temperature.  Chemical: basic water quality attributes (pH, dissolved oxygen) as well as a wide range of micropollutants (metals, herbicides, pharmaceuticals, etc.).  Biological: harmful bacteria (E. coli) as well as community-based metrics that are indicators of biological integrity (aquatic insects & fish).

Answer 14

In urban environments, the presence of impervious surfaces (roofs, pavement) prevents infiltration of rainwater into the ground and results in rapid runoff. High runoff during storm events results in unnaturally high streamflow conditions. These cause stream bank and bed erosion. Erosion of bed and bank materials results in high mortality of fish and aquatic insect communities, and results in the export of sediment to downstream areas (lakes, estuaries).

Answer 15

Urban streams have a “flashy” hydrograph (rapid changes in water level & discharge) due to runoff from impervious surfaces. Consequences: stream erosion and incision. Example: water level in Reedy Creek.

Answer 16

High discharge during storm events  Channelization & incision  Homogenization of habitat & Reduced biodiversity  Loss of ecological function

Answer 17

Human activities can alter stream temperature both directly (e.g., discharge of heated effluent, loss of riparian shading) and indirectly (via rising air temperatures). These may cause stream conditions outside of thermal tolerance for aquatic organisms. Stream shading provided by mature, young and post-burn forest. Loss of shading may arise from timber harvesting or clearing of land for agriculture or development.

Answer 18

A measure of the ability of water to carry an electrical charge. Conductivity is directly related to the amount of dissolved substances in water. Elevated conductivity in streams is often an indicator of pollution

Answer 19

Road salt runoff results in elevated levels of stream conductivity and chloride following snowfall events in city of Richmond. Salinization of freshwaters is a widespread problem: impacts on aquatic life, drinking water sources. How to balance human risk (safe roads) and ecological harm?

Answer 20

Dissolved oxygen is an important water quality attribute as many species are intolerant of low oxygen conditions. Oxygen concentrations in water are determined in part by temperature (solubility). Low oxygen conditions in streams may be indicative of organic matter pollution (e.g., sewage). Organic matter is decomposed by bacteria which consume oxygen in the process.

Answer 21

Wastewater treatment plants and other industries may discharge effluent that when released into the environment causes oxygen depletion. COD = chemical oxygen demand. Presence of reduced chemical compounds (e.g., NH4) results in oxygen consumption as these are oxidized (e.g., NO3). BOD = biological oxygen demand. Dissolved and particulate organic matter that is decomposed resulting in oxygen consumption by bacteria.

Answer 22

A long list of potential chemicals of interest.  Naturally occurring substances that may be present in excess amounts: e.g., sediments, mineral nutrients (nitrogen, phosphorus), trace metals (Al, Zn, Cu).  Man-made compounds that do not naturally occur in the environment: PCBs, herbicides, pesticides, pharmaceuticals, microplastics.

Answer 23

Escherichia coli (E. coli) - a coliform bacterium found in the lower intestine of warm- blooded organisms. Most strains are harmless, but its presence in the environment is indicative of fecal contamination.  The presence of E. coli poses a hazard to human health, particularly in drinking water, but also through recreational contact.  Sources include sewage, urban runoff (pet waste & wildlife) and agricultural runoff (livestock operations).  Water samples are incubated under specific conditions to determine the number of colony forming units (cfus).

Answer 24

In cities which have combined sewer systems, rain events result in the release of wastewater to the environment.

Answer 25

E. Coli levels exceeding 126 cfu are considered unsafe for recreational contact.

Answer 26

Poor water quality results in a loss of biodiversity as sensitive species are unable to survive and reproduce and communities become dominated by tolerant species.  Biota are often used as indicators of water quality: diverse, balanced communities of stream insects and fish are indicative of good water quality conditions.

Answer 27

Advantages of biomonitoring: Aquatic communities can be used to directly assess whether conditions are suitable for aquatic life. Biota integrate the effects of stressors over their life span, thereby providing a longer-term perspective on the suitability of the site to support aquatic life (vs. spot sample of chemistry). Disadvantages of biomonitoring: Requires skilled taxonomists to identify fish, insects, algae (not automated, more difficult to replicate, more expensive vs. chemistry). Does not provide information on stressors (what is the cause of the impairment to aquatic life?).

Answer 28

Algae: planktonic and attached species used in assessment of lakes and streams, respectively.  Benthic macroinvertebrates: bottom-dwelling animals (many are insects) that can be seen without magnification.  Fish: long-lived and more mobile (integrate conditions over greater space and time).

Answer 29

Individuals:  Species-specific tolerance to pollution  Health: presence of lesions, abnormalities, body condition. Communities:  Diversity: number of species present, relative proportions of individuals.  Functional groups: e.g., insect scrapers, shredders, grazers, predators, etc.  Number of native vs. invasive species

Answer 30

Maccaffertium- flatheaded mayflies, relatively pollution intolerant.  Fast-water specialists (riffles) that cling to hard substrate and feed primarily by scraping algae (diatoms).  Disturbance that reduces flow, and sedimentation that buries rocks and benthic algae are primary stressors.  DEQ tolerance value is 5.4/10 (pollution sensitive taxa have values <3).

Answer 31

Typically carried out by electrofishing – a weak current is used to immobilize and capture fish. Individuals are identified in the field and released. Generally harmless, though can cause mortality in very small fish. A representative sample of the fish assemblage is obtained by collecting from a length of stream with a mix of habitats (e.g., pools and riffles).

Answer 32

Cause of impairment: bacteria (from livestock), sediment (erosion), ag chemicals (fertilizers, pesticides, herbicides). Install fencing to keep livestock out of streams Maintain riparian plant buffer to remove pollutants No-till farming to reduce erosion & sediment transport

Answer 33

Cause of impairment: bacteria (from sewer overflows), elevated salinity (from road salt), bed & bank erosion (from stormwater runoff). Install stormwater retention ponds & rain gardens to capture runoff & promote infiltration Eliminate overflows from sewer systems Restore riparian buffers

Answer 34

Catchment-based approaches have the advantage that they treat the problem at the source (reduce run-off and pollutants before they enter the waterway). The challenge is that they are generally very limited in scope relative to the scale of the problem (can’t fix entire catchment). Consider a 3-mile stream in an urban setting – many property owners (private, public, business). What proportion are willing to undertake (pay for) or allow installation of green infrastructure?  In-stream restoration can be used to repair degraded stream channels. but will repairs succeed if proximal causes (livestock, impervious surfaces) are not addressed?

Answer 35

Typically focus on the physical template of the stream channel.  Field of dreams hypothesis: if you build it, they will come (i.e., if stream habitat is returned to a more natural condition, stream biology and functioning will return).  How do we measure success? The goal of restoration is usually not to return the stream to a pristine state (difficult to achieve in ag or urban setting), but to stabilize the stream to prevent further degradation (bed and bank erosion).

Answer 36

A riffle-pool sequence develops as a stream's hydrological flow structure alternates from areas of relatively shallow, fast-moving water to deeper, slow-moving water. The sequence commonly occurs at intervals of from 5 to 7 stream widths.  Meandering streams tend to develop a riffle-pool sequence with pools in the outsides of the bends and riffles in the crossovers between one meander to the next.  Habitat diversity fosters biodiversity Examples of pool vs riffle fishes  Fishes and aquatic insects have specialized habitat preferences  Greater habitat diversity results in greater biodiversity  Loss of habitat diversity (urban streams) results in loss of biodiversity

Answer 37

1 km of stream returned to its floodplain  During storm events, water exceeds bankfull capacity and spills into floodplain  Floodplain inundation slows down the water, more opportunity for removal of sediments, nutrients and other pollutants  Meanders and Pool-riffle structure enhances in- stream habitat diversity and biodiversity  Longer transit time of water through the stream channel allows greater opportunity for nutrient uptake by benthic biofilm communities.

Answer 38

Benefits Supporting aquatic life designated uses by increasing habitat diversity to foster greater biodiversity Enhancement of stream functioning by slowing downstream transport of water and reducing sediment and nutrient fluxes. Trapping of particulate matter within the floodplain during storm events. Greater transient storage within the stream and floodplain allows for uptake of dissolved inorganic nutrients by biofilms.

Answer 39

Changes in stream hydrology resulting from urbanization: Before - rainwater infiltrates soil and is slowly discharged to the stream. Small peak flows following storm events. After - impervious surfaces (roads, rooftops) generate rapid runoff. Large peak flows after storm events.

Answer 40

Flood stage: when stream water elevation exceeds bankfull capacity. Before urbanization: water escapes channel and inundates lateral floodplain areas. This reduces the force of water and results in sediment deposition and storage in the floodplain. After urbanization: streams become incised, as bank height increases, water is prevented from escaping into floodplain. Erosive force increases resulting in greater incision and downstream sediment transport.

Answer 41

Key challenges: impervious surfaces generate stormwater runoff.  High discharge during storm events causes stream bank and bed erosion  Channelization & incision results in loss of habitat complexity and Reduced biodiversity  Loss transient storage and floodplain connectivity reduces ecological function (sediment trapping and nutrient uptake).

Answer 42

Historically focused on getting rid of water (to prevent flooding).  Streams were channelized (straightened and deepened) and sometimes lined in concrete – designed to convey water quickly.  Some streams diverted to underground culverts to allow for development.  How to un-do this in an urban setting (engaging private landholders)?

Answer 43

Not in my backyard: re-grading incised stream banks requires earthmoving, which often requires removal of riparian trees. Trees are re-planted following construction, but it may take >20 years for forests to recover. This has led to opposition from local homeowners (e.g., cancellation of Reedy & Rattlesnake creek projects in Richmond).  Does is work? Is there evidence that stream restoration achieves stated goals (e.g., improving stream biodiversity and ecological functioning)?  Some projects successful (e.g., Wilson Creek), others not, most are not monitored.  Assurance of success if especially important where nutrient reduction credits are given.

Answer 44

The EPA has prescribed a “pollution diet” for the bay, which sets limits on sediment, N and P inputs.  States are required to implement mitigation activities to meet their pollution targets.  Mitigation activities for point sources (e.g., factories & wastewater treatment plants) provide quantifiable results (e.g., lbs of N and P removed).  Mitigation activities for non-point (diffuse) sources do not provide quantitative results. Examples: stream & wetland restoration, no-till ag, stormwater retention basins, etc.  If we give nutrient reduction credits for best management practices (BMPs) that don’t actually work, then we are not achieving actual nutrient reductions.

355 exam 1 Flashcards

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