Considering multiple stressors Flashcards
(26 cards)
What other drivers of change affect marine organisms and ecosystems (other than OA)?
- Global warming
- Fishing
- Pollution
- Mining
- Hypoxia
- Eutrophication
- Habitat loss
- Species invasions
How much have the oceans increased in temperature in the last 100 years?
Increased by 0.6 - 0.76 dC
How much is the ocean likely to heat by over the next 100 years?
Likely to increase by up to 7 dC
How much of the ocean was observed to be impacted by cumulative effects in 2013?
Pretty much the whole ocean.
What did the combined impacts of increasing CO2 and warming have on starfish (Pisaster ochraceaus)? What did this suggest?
- Feeding and growth rates increased under warming and high CO2
- Calcification reduced slightly under warming conditions
When in high-food conditions, organisms can withstand environmental warming through up-regulated feeding.
Which species were used to test the combined effects of CO2, warming and invasive species on barnacle larvae?
Semibalanus balanoides (native)
Elminius modestus (invasive)
How did growth rates vary under combined conditions for invasive vs native barnacle larvae?
- Invasive -> Warmer conditions didn’t affect growth rates alone, but slightly decreased when combined with high CO2
- Native -> Significant change in growth rate at higher temperatures - decline at normal pH with increasing temp., but an increase at lower pH 7.7 with increasing temp.
Greater error bars for native species = greater variation.
How did the calcium content vary under combined conditions for invasive vs native barnacle larvae?
S. balanoides calcium content reduced at high temperatures & CO2
No effect on E. modestus
How did the survival vary under combined conditions for invasive vs native barnacle larvae?
S. balanoides survival reduced at high temperatures and CO2
No effect on E. modestus
Overall, which of the native or invasive barnacle larvae is better suited for combined effects of OA and rising temperatures?
Invasive species (less affected in terms of survival, calcium content and growth)
What was identified when studying the long term effects of combined temperature and pH/CO2 effects in Alitta virens?
Seasonal cycles of bioturbation broke down under warming scenarios - this was driven by temperature, which was a more dominant effect that the OA condition alone.
This, in turn, affected nutrient cycling (and water column nutrients).
How does the fact that behaviour in Alitta virens follows a seasonal pattern affect the significance of climate effects?
This can amplify the effects on Alitta virens, with a breakdown in seasonal rhythm driving changes to crucial processes such as nutrient cycling.
How did the combined effects of hypoxia and OA affect newly bred embryos of Menidia menidia (Atlantic silverside)? Which isolated effect (hypoxia or OA), did this more closely follow?
Under low DO and low pH:
- Longer hatching time
- Hatching success and post-hatch survival decreased
- Standard length was much smaller
This typically followed observations for low DO (low pH was closer to the control).
Which variables can be measured to understand benthic ecosystem functioning?
- NH4 -N (ammonium)
- NOx -N (nitrate/nitrite)
- PO4 -P (phosphate)
What was observed in terms of functional group distribution under pH and temperature stress in benthic sediment cores?
Functional group composition changed depending on sediment type, and the effects of environmental stressors varied across sediment types.
Mixed sediments showed less pronounced changes.
What are the two main response variables measured to assess climate impacts on benthic communities?
- Species behaviour (e.g., sediment reworking, bioirrigation, surface boundary roughness)
- Ecosystem functioning (e.g., nutrient generation and cycling)
Besides the climate treatment, what other factor influenced benthic community composition and functioning?
Season or time of year — due to differences in organismal fitness, life stage, and environmental sensitivity.
Which season is thought to be most affected by environmental change in terms of benthic communities? Is this well-sampled?
Winter - altho not well sampled (most occurs in summer, meaning this vulnerability may not be properly estimated).
How did seasonal timing (March vs August) influence nutrient cycling in the benthic experiment?
March = nutrient generation was lower (linked to changes in functional group composition)
August = warming caused shallower mixing but increased nutrient release, showing season-dependent responses
Why is it important to include seasonal variation in long-term benthic climate studies?
Because organismal responses vary with season, and winter may be the most climate-sensitive period — ignoring seasonality may misrepresent impact severity.
What effect did the combo of high trawling intensity and warming have on species richness in benthic communities?
There was a significant decline in species richness, especially under high trawling + future climate conditions.
How did benthic community composition respond to the combo of trawling and climate stress?
Species composition shifted, reflecting both trawling intensity and climate treatment.
What happened to nutrient concentrations under high trawling and future climate conditions for benthic communities?
Nutrient concentrations were reduced, suggesting disrupted biogeochemical cycling.
Which had a greater impact on macrofauna and nutrient cycling in benthic communities: climate change or trawling?
Future climate conditions had a greater overall impact than trawling frequency.
