Minimal if at all. Tent's purpose if to protect from the elements (wind and rain). The difference in warmth between a bivy vs an arena is inconsequential.
If you are concerned WRT to the warmth of your sleeping bag, consider a bag liner (if you can source Alpha direct, you can get a surprising amount of additional insulation at low cost/weight/volume).
Other avenues include: (1) purchase a warmer bag; (2) purchase a quilt to drape over your bag; (3) wear (dry) clothing, perhaps long johns, a puffy, down booties, warm beanie
Low 40s is still quite comfortable. Most sleeping bags will be enough (what's your bag rating?). Personally I'd consider a liner (helps keeping your bag clean) and wearing additional clothing: puffy vest + beanie + warm base layer, top and bottom. should keep you warm.